Smart viruses that jump species: Covid-19, HIV, Ebola and others…


By Ricardo Ribas

Image from syaibatulhamdi,
Image from syaibatulhamdi,

Viruses are microscopic agents that infect living organisms and cause diseases. They are considered the most abundant biological entity on the planet, existing for over 1.5 billion years. Viruses have both life and non-life properties. They do not have cells and cannot turn food into energy, but have genetic material (either DNA or RNA). Without a host cell, viruses are inert containers of chemicals so they need to infect cells in order to reproduce, evolve and survive. Hosts can be humans, animals, plants, fungi and bacteria. Some viruses are harmless whilst others cause diseases, some of which leading to the death of the host. To date there are no drugs capable of killing viruses so the host is dependent on its own immune system to fight the infection. Nowadays, there are some antiviral drugs capable of inhibiting them from reproducing and developing, as well as vaccines able to prevent infections and control the spread of the disease.

There are many types of viruses, each one adapted to its own host, but at times, viruses can jump and infect different hosts through a process called “spillover”. This can happen as a result of increased contact between different species or due to mutations that allows the viruses to evolve and gain the capacity to spread more efficiency in order to survive and to become more dangerous. In recent years, we have heard more and more about viral diseases able to jump from animals to humans. Here are some examples:

Influeza: The Flu Viruses

In the last century, there have been many examples of flu-like diseases caused by viruses that jumped from animals to humans. Some are caused by influenza viruses, a family responsible for attacking the respiratory system and causing flu like symptoms in humans.

In 1918, a deadly flu-like pandemic (Spanish Flu) appeared and rapidly spread around the world, infecting 500 million people and killing an estimated of 50 million. There is still some controversy about where the virus was originated from since Europe, America and Asia were affected simultaneously, but recent studies tend to agree that the outbreak may have originated in the North of China, either from pigs or from domestic and wild birds.

But there are other more recent examples of influenza viruses that jump species, such as the ones responsible for the outbreaks of swine-flu and bird-flu.

Although pig’s influenza viruses are rarely transmitted to humans and are hardly spread between people, they were responsible for the worldwide outbreak of swine-flu in 2009-2010. The disease was firstly identified in 2009 when many cases of human respiratory illness were reported in Mexico. We now know that this virus is the result of a merge between genetic material from pigs, birds and human viruses. In animals, the disease is responsible for fever, coughing, nose and eyes discharge, sneezing, breathing difficulties and lack of appetite, however, some animals show no signs of illness. Humans show flu like symptoms and can be infected either by close contact with pigs through farming and fairs or by person-to-person contact during sneezing, coughing and by contaminated surfaces. Fortunately, the 2009 outbreak was not as serious as previously anticipated and only a relatively small number of cases lead to serious illnesses and deaths. Swine flu is now considered a normal type of seasonal flu and is included in the vaccination program.

Bird-flu is another infectious type of influenza that spreads among wild and domestic birds. The most common form of the disease is caused by H5N1, a deadly virus for birds. H5N1 was firstly identified in humans in Hong-Kong in 1997. Human cases of the disease were linked with the handling of faeces, nasal and mouth secretions of infected poultry, particularly in farms and markets. Bird symptoms include: sudden death, lack of coordination, purple discoloration of the wattles, combs and legs, misshapen eggs, diarrhoea, nasal discharge, coughing and sneezing. Humans generally suffer from fever, cough, sore throat, muscle ache but the disease can lead to pneumonia. The disease has high mortality rate and is responsible for causing the death of about 60% of those infected. The good news is that H5N1 only rarely infect humans and is not capable to spread from person to person. In spite of this, it is a fast mutating virus and if it gains the capacity to be transmissible between humans while retaining its capacity to cause severe disease, the consequences can be very serious.

Human Immunodeficiency Virus (HIV): one century with humans

Another example of a virus that crossed species is the one responsible for human immunodeficiency. Once infected, the virus attacks the immune system of the host, opening the door for other opportunistic diseases. This disease was first observed in 1981 in the USA, but scientists believe that humans got infected in the 1920’s in West-Central Africa, possibly in what is now the Democratic Republic of Congo. Scientists believe this happened when hunters consumed meat from non-human primates carrying a virus closely related to the HIV (Simian Immunodeficiency Virus or SIV), a virus that also attacks the immune system of these animals. It is suspected that the infection has reached the Caribbean islands in 1960s, New York City in the 1970’s and San Francisco a decade later, when it was finally discovered.

Ebola, the terrifying virus

The Ebola virus was first discovered in 1976 near the Ebola River in the Democratic Republic of Congo. Since then, the virus has been responsible for occasional outbreaks in human and primates in many African countries. Between 1976 and 2013, the world health organisation reported 24 human outbreaks of the disease with 1.600 deaths in total, but the largest outbreak occurred between 2013 and 2016 and was responsible for over 11.000 deaths. The disease is rare but very severe, often causing fever, sore throat, body aches, vomit, diarrhoea and sometimes bleeding inside and outside the body, with death occurring in 50% of the human infected. Scientist think that the Ebola virus may be carried by bats, because these animals don’t die of the disease. It is believed that humans get infected by contact with the infected animal’s body fluids, either directly from bats or during consumption of nonhuman primates. The virus spreads through human-to-human contact and it is also possible via blood or the body fluids of the infected person.

Coronaviruses repeated stories

Recent history also showed us how coronaviruses can jump from animals to cause a large number of human deaths. Coronaviruses are a large family of viruses known to exist for over 10.000 years. Its name derives from the latin word “corona”, that means crown due to the presence of crown-like spikes in their surface.

Coronaviruses are responsible for respiratory and intestinal diseases in mammals and birds, but the symptoms vary according to the host animal and the type of virus. For instance, in chickens, coronavirus attacks the respiratory and urogenital tracts, whilst in dogs, cats, ferret, rabbits, turkeys, pigs and cows the virus tends to affect the animal’s intestine leading to diarrhoea.

Humans, can only be infected by seven types of coronaviruses. Four of these are very common and responsible for mild respiratory infections with symptoms similar to the ones observed with a cold, but the remaining three viruses can lead to serious and sometimes lethal respiratory infections, such as pneumonia. These include the viruses responsible for the Severe Acute Respiratory Syndrome (SARS), the Middle East Respiratory Syndrome (MERS) and the most recent outbreak in China in 2019-2020 (Covid-19).

SARS was first identified in Southern China during the outbreak of the disease in 2003. Scientists believe that bats are the reservoir of the virus and that the disease was transmitted to humans through consumption of civet cats meat infected by the bats. Once in humans, the disease can spread from person to person. By the end of the outbreak, over 8000 people have been infected and approximately 10% of those died (774 people). Fortunately, no cases of SARS have been reported since 2004.

MERS was reported for the first time in 2012 in Saudi Arabia. It is known that the virus was firstly transmitted to humans by dromedary camels in the earlier 2010s, possibly during consumption of camel meat. This virus has also been found in bats and is believed that it may have infected camels in Africa in the 1990s. Even though the possibility of human to human transmission is very low, the mortality of the disease is quite high standing above 35%. So far, MERS killed 858 out of the 2494 reported cases since it appeared in 2012.

Very recently a new outbreak of coronavirus has emerged in Wuhan, China (Covid-19). Similarly to SARS and MERS, this infection is also responsible for severe acute respiratory infection that can lead to severe organ failure, septic shock, blood clots symptoms and eventually death. Since this is a very recent virus, not much is known about it yet. To date scientists haven’t yet identified which animal the reservoir for the virus is, however, it appears that the contamination to humans may have occurred in a wildlife market, possible during consumption of wild animals. Despite the fact that the rate of transmission between humans is high, the mortality rate seems low. Since it’s origin, the disease has spread all over the world.

When human viruses infect animals?

Sometimes viruses can jump the opposite way. There are also examples of human viruses that alter and adapt to infect animals. This is the case of the human respiratory syncytial virus (HRSV) and the human metapneumovirus (HMPV) that have jumped from humans to chimpanzees. It is believed that this has occurred between 1999 and 2006 in West Africa possibly through tourists visiting the area. Whilst these viruses rarely cause severe disease in healthy adult humans, they are responsible for outbreaks of respiratory diseases among African chimpanzees leading to the death of entire populations.

Why are animal-derived outbreaks getting more frequent?

The fast-growing world population and the development of large metropolis are incentives to the expansion of wildlife trade, which favoured diseases to spill over from animals to humans. Additionally, environment and climate changes are shifting animal habitats, altering their life-styles, their geographic locations and their eating habits (who eat whom). Finally, in an era of international travel means that diseases can spread very quickly.

But a question remains. In a world more vulnerable than ever to new animal-borne diseases, what do you think can be done to prevent future outbreaks?

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

Reference Sources

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The subjects and ideas discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Monkeypox, a new health scare?

As the world unwinds from Covid-19, a new scare knocks at our door, monkeypox. Could this viral disease become the next pandemic? Learn more about this disease and its capacity to jump from animals to humans.

By Ricardo Ribas

Image from geralt,

What is Monkeypox?

Monkeypox is a rare viral infectious disease that affects both animals and humans. The agent, an Orthopoxvirus, is an enveloped double-stranded DNA virus usually endemic in the tropical forests of Central and West Africa and a close relative from the smallpox viruses, a family with a tendency to attack skin cells. Monkeypox is not a recent disease, the virus was first identified in 1958 in laboratory monkeys in Denmark and subsequently in humans in the 1970s in the Republic of the Congo. In contrast to what the name indicates, the natural reservoir of this virus is not the monkey and scientists are still unsure which animal would be, but there are some indications that it might be a rodent. It is known, however, that the monkeypox virus can affect a broad range of animals including rope squirrels, Gambian pouched rats, mice, dormice, non-human primates and humans. There are two known types of monkeypox in humans: one predominantly found in West Africa and responsible for a mild disease (with a fatality rate of about 3-4%) and a second one prominent in Central Africa (Democratic Republic of Congo) and responsible for more severe disease with a fatality rate reaching 10%. Recent studies confirmed that the 2022 outbreak is related to the West African variant and as of the date of this publication, no deaths have been recorded during the current outbreak of the disease.

How is monkeypox transmitted?

The routes of transmission from animals to humans is usually by direct contact with blood, body fluids and the cutaneous lesions (blisters and scabs) as well as by the consumption of uncooked meat or other products from infected animals.

Infection between humans is often a result of sharing clothing, bedding and towels used by someone infected with the virus particularly when suffering from rashes, blisters and scabs. Contamination is also possible through droplets of respiratory particles during coughing or sneezing. Recent research also suggests the possibility for vertical transmission between mother-to-child.

Given the high frequency of human to human transmission observed in the current outbreak of the disease, together with the fact that most of the patients are young adults and middle-aged men who have sex with men, scientists suspect that the close contact during sexual activities might be the main route of transmission. It is, however, important to note, that monkeypox is not a sexually transmitted disease.

Image from SamuelFrancisJohnson, pixabay.con

So, what are the symptoms?

The incubation period for monkeypox (time between the infection and the appearance of the first symptoms) is between 5 to 21 days. In the first stages, the person will show fever, headache, muscle aches, shivers, swollen gland and tiredness, followed by a rash a few days later. The rash is characterized by the presence of raised spots often starting in the face and later spreading throughout other parts of the body and genitals. The spots eventually turn into small blisters filled with liquid and then into scabs that will fall off within a few weeks. The duration of the symptoms are approximately 2-4 weeks.

Children, immunocompromised individuals and pregnant women are more susceptible to develop severe forms of the disease as well as to suffer complications and a higher fatality rate. Scientists are still not sure why the 2022 outbreak is causing milder symptoms than previously observed, but it may relate to the fact that the virus is infecting a healthier and stronger population (mainly men between 20-50 years of age), from countries with better health care systems than previous outbreaks. There is no evidence that the virus has mutated to become less deadly.

How to treat the disease?

The great majority of people infected will recover from the disease without requiring any specific therapy. However, in severe cases involving immunocompromised patients, pregnant women and children, additional therapy may be required. There is currently no specific treatment approved for monkeypox, but a series of antiviral agents developed for patients suffering from smallpox might be effective. Administration of smallpox vaccines also appear to reduce the severity of the disease and should be consider in the most serious cases.

How to prevent from catching monkeypox?

A series of recommendations are important to keep in mind to prevent infection from monkeypox:

• Avoid direct contact with animals infected with the disease or with any of their derived products, such as blood and uncooked meat,

• Avoid contact with any materials that have been in contact with infected animals or humans,

• Thoroughly cook all foods containing animal meat or their parts before eating,

• Humans infected with monkeypox should isolate until all the symptoms are over and the scabs have fallen off,

• Use protective equipment and practice good hygiene (such as wash the hands with soap and water or hand sanitizer), particularly if in contact with infected animals or humans,

• Professional health workers should implement standard infection control precautions,

• Smallpox vaccines appear to be 85% effective against monkeypox and it can be used as a post-exposure prophylaxis for close contacts of known cases,

• Preferably select people already vaccinated against smallpox to care for animals and patients infected with the disease.

• The governments should improve regulations for animal trade and importation of rodents and non-human primates, such as promotion of isolation and quarantine of animals.

New Outbreak 2022

Monkeypox is generally a mild disease, confined to Central and West Africa, often endemic in Benin, Cameroon, Central African Republic, Democratic Republic of the Congo, Ghana, Ivory Coast, Liberia, Nigeria and Sierra Leone. While it is not the first time that monkeypox spreads to regions outside Africa, this is quite rare. For instance, in 2003, the West African strain managed to reach 70 humans in the United States. This was linked to the direct contact of humans with infected pet prairie dogs who have been housed with Gambian pouched rats imported from Ghana. All 2003 cases resulted from an animal to human contact and there was no evidence of human to human transmission.

The recent 2022 outbreak appears to be the result of the importation of the disease through infected humans with the first case reported in England in an individual recently arrived from Nigeria. As of the day of this publication, more than 1300 cases have been reported throughout Europe, North America, Middle East and Australia, the majority of which as a result of human to human transmission particularly affecting men who have sex with men. Scientists are trying to understand the reason for the spread of the disease outside Africa but are concerned that human monkeypox virus may have already been established as a reservoir in non-African wildlife species creating the perfect environment for future outbreaks and the opportunity for the virus to mutate to more dangerous and transmissible variants.

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and scientific researcher.

Reference Sources

1. Monkeypox, Wikipedia, Wikipedia Foundation, June 2022,

2. 2022 monkeypox outbreak, Wikipedia, Wikipedia Foundation, June 2022,

3. Monkeypox, WHO, June 2022,

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5. Monkeypox. Centers for Disease Control and Prevention. June 2022.

6. Monkeypox: Cases outside Africa rise to 780 in three weeks. BBC News. June 2022.

7. Daniel Payne & Carmen Paun. What researchers do — and don’t — know about monkeypox. Politico. June 2022.

8. Camille Besombes. Monkeypox: ‘This is an entirely new spread of the disease’. The Conversation. June 2022.

9. Jon Cohen. Concern grows that human monkeypox outbreak will establish virus in animals outside Africa. ScienceInsider. June 2022.

10. Jonathan Wolfe, Monkeypox: a Guide. The New York Times, June 2022.

11. Jason Gale. Understanding monkeypox and how outbreaks spread. The Washington Post. June 2022.


The subjects and ideas discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Toxoplasmosis: Be aware of your cat and uncooked meat

Learn about toxoplasmosis, a worldwide and common parasitic disease responsible for serious problems in pregnant women and those with weakened immune system.

By Ricardo Ribas

Image from ThomasWolter,

Toxoplasmosis is a world distributed disease affecting warm-blood species such as birds, mammals and humans. The agent is a single-celled protozoa parasite named Toxoplasma gondii. Whilst studies suggest that the Toxoplasma can be found in approximately 30% of the human population, the disease is rarely a reason of concern in healthy individuals, but can lead to serious consequences in those with weak immune system, such as AIDS sufferers or those undergoing chemotherapy. Pregnant women are also vulnerable and the disease can lead to miscarriage, stillbirth and devastated neurological problems to the foetus.

How is Toxoplasma transmitted?

Most of human and animal infections occur during the consumption of uncooked meat containing toxoplasma cysts or by ingestion of food/water contaminated with eggs. Other less common routes of transmission include blood transfusions, organ transplantation and vertical transmission from the mother to foetus. The World Health Organisation suspects that, just in Europe, there are over a million toxoplasma infections happening each year.

The Toxoplasma’s life cycle

Cats and other felines have a crucial role in the life cycle of the Toxoplasma’s given that they are the only species able to provide the right environment for the parasite to mature sexually and complete its life cycle. The process starts when the felines consume meat (often rodents, birds, and other small animals) carrying the parasite cysts. The cysts will travel to the animal’s stomach where they lose the protective envelop, triggering the start of the process of maturation and replication. Once reach the intestines, the toxoplasma produce eggs that are subsequently released into the environment with the animal’s faeces.

The eggs can remain in the environment for several years and are been able to contaminate food and water. Once ingested by animals or humans, the eggs have the potential to migrate through their bodies and lodge in the form of cysts in many tissues, such as brain, muscles, liver, heart, lungs, eye, etc, generating a new route for transmission to other species that will consume these tissues. Infection during pregnancy is of particular concern both in animals and humans, because the parasite has the potential to trespass the placenta and to lead to the development of neurological problems in the foetus, stillbirth and miscarriage.

What are the symptoms?

While most of the infections by Toxoplasma do not cause any symptoms in healthy animals and humans, complications often occur in pregnant females or individuals with weaken immunity. This is because the toxoplasma is an opportunist parasite that takes advantage of hosts with weakened immunity to spread. In the majority of the cases, people show flu-like symptoms such as fever, tiredness, muscles-ache, lack of appetite and weight loss. However, complication can happen depending of the organs affected. These can include diarrhoea, vomiting, jaundice, coughing, difficulty breathing, pancreatitis, headaches as well as problems in the nervous system and with the eye (reduced or blurred vision, eye pain, redness or tearing) and occasionally death. Recent studies have also suggested a link between Toxoplasmosis and schizophrenia and suicide. Finally, particular care should be given during pregnancy because it can bring catastrophic consequences to the foetus and lead to stillbirths or birth defects such as mental retardation, blindness, hydrocephalus – presence of water in the brain, seizures, etc.

And how can we treat?

Whilst most animals and humans often recover without any specific treatment, in some cases this is required. A combination of antibiotics and antimalaria drugs are usually recommended in animals and humans to prevent serious complications. Depending on the specific symptoms, a selection of other treatments may be required, such as the use of corticosteroids for those suffering from eye problems.

Preventive Measures

• Ensure meats are well cooked, fresh vegetables are washed thoroughly and avoid consuming unpasteurized milk or any products made from it.

• Avoid handling raw meats without gloves.

• Wash utensils and surfaces that may have been in contact with raw meats to avoid contamination with other foods.

• Clean the garbage daily using disposable gloves.

• Wear gloves and wash your hands thoroughly after handling or cleaning cat faeces. Disinfect the places where the cat may have defecated.

• Prevent cats from eating raw meat or any animals such as mice or birds.

• Avoid touching or handling pregnant sheep or lambs.

• If you intend to become pregnant, it is advisable to take a toxoplasmosis test. If the test is positive, it means that you are already immune. If the test is negative, take extra precautions to prevent infection during pregnancy.

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and scientific researcher.

Reference Sources

1. Toxoplasmosis. Wikipedia. Wikipedia Foundation. Accessed May 2021.

2. Parasites – Toxoplasmosis (Toxoplasma infection). Centers for disease control and Prevention. Accessed May 2021

3. Toxoplasmosis. Fact Sheet. World Health Organisation. Accessed May 2021

4. Toxoplasmosis. NHS. Accessed February 2021.

5. Bigna JJ, Tochie JN, Tounouga DN, Bekolo AO, Ymele NS, Simé PS, Nansseu JR. Global, regional and national estimates of Toxoplasma gondii seroprevalence in pregnant women: a protocol for a systematic review and modelling analysis. BMJ Open. 2019 Oct 19;9(10): e030472.

6. Dubey, JP; Lindsay, DS; Speer, CA. Structures of Toxoplasma gondii Tachyzoites, Bradyzoites, and Sporozoites and Biology and Development of Tissue Cysts. Clin Microbiol Rev. 1998 Apr; 11(2): 267–299.

7.Montoya JG, Liesenfeld O. Toxoplasmosis. Lancet 2004; 363:1965- 76.

8. Dickerson F, Stallings C, Origoni A, Katsafanas E, Schweinfurth L, Savage C, Khushalani S, Yolken R. Antibodies to Toxoplasma gondii and cognitive functioning in schizophrenia, bipolar disorder, and nonpsychiatric controls. J Nerv Ment Dis. 2014 Aug; 202(8):589-93.

9. Cook TB, Brenner LA, Cloninger CR, Langenberg P, Igbide A, Giegling I, Hartmann AM, Konte B, Friedl M, Brundin L, Groer MW, Can A, Rujescu D, Postolache TT. “Latent” infection with Toxoplasma gondii: association with trait aggression and impulsivity in healthy adults. J Psychiatr Res. 2015 Jan; 60:87-94.


The subjects and ideas discussed on this article are for informational purposes only. For more information consult a doctor, a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

The astonishing reproductive life of the animals

The animal kingdom is extremely diverse consisting of a wide-range of anatomies and behaviours. In this article, we will explore the scientific reasons for some of the mind-blowing strategies developed by some species to court, reproduce and produce offspring. Some will leave you speechless!

By Ricardo Ribas

Image from Pexels,
Image from Pexels,

1. Males that get pregnant!!

Seahorses, pipefishes and seadragons have a very peculiar and different reproductive strategy, as they are the only fishes to undergo male pregnancy. Depending on the specie, the males have a pouch located in the abdomen or in the tail where the females deposit the eggs during mating. It is in the male’s pouch that the sperm fertilise the eggs and it is the male’s responsibility to carry and develop the fertilised eggs for a period between 9 and 45 days. The male pouch functions similarly to the mammal’s and human’s placenta, providing protection, the nutrients and the oxygen necessary for the fish development as well as the structure necessary to get rid of the waste products. By the end of the pregnancy, the males can deliver between 5 and 2000 young fish.

2. Sexual Cannibalism

Some animals use reproductive strategies resembling horror movies. Take as an example the family of black and venous spiders, commonly named as black widows as a result of the females’ gruesome behaviour of killing and eating the males after mating. Scientists believe this form of sexual cannibalism appear to provide the females with an extra source of proteins increasing their chance for reproductive success and offspring survival. Studies have also shown that females who practice this type of cannibalism produce larger eggs and healthier offspring with a better chance of survival, than the females that don’t eat the males. Understandably, some males prefer to court females that have already eaten, even if they are less fertile and fruitful. Scientists believe the males are able to tell how hungry the females are by the presence of pheromone smells in the silk of their cob webs.

There are other examples of sexual cannibalism in nature, such as is the case of the mantises, where females also kill and eat the males during mating. Whilst the purpose for their behaviour is still unknown, studies shown that females with poor diets are more likely to eat their partners, and that, similarly to spiders, it appears to provide them with extra nutrients necessary to improve the chances of reproductive success.

3. Transsexual animals

Other species have the astonishing capacity to change sex throughout lifetime. All clownfish are born male but they carry both male and female reproductive systems. Their school is composed by one female, often the larger animal in the group; a dominant breeding male, usually the second biggest in the group; and several immature males. When the female dies or disappears, the dominant males starts a process of sex change taking about 45 days to be complete, during which the male hormones are inhibited and the female hormones are activated. At the same, one of the immature males becomes the dominant male. Scientists believe this sex-change capacity allows the clownfish to remain in their habitat, circumventing the need to travel and risk their life to find females to mate. Wrasses use the same sex-change strategy as clownfish but in the opposite way. In this case, is the larger female of the group that changes sex and transforms into a male, taking the role of the previous dominant male of the harem upon his death or disappearance.

4. Inflated balloons to attract females’ attention

Male dromedary camels have a very strange and peculiar way to attract females. They hold an organ located in their throat that once inflated turns into a giant pink balloon (often confused with the tongue) that hangs and dangles from one of the sides of the male’s mouth to show their dominance and to attract females. This organ is called dulaa, what means “soft-palate” in Arabic. Male seals have a similar organ also used for sexual attraction and territorial fights, however, in their case, this large pinkish inflated balloon-like sac appears from the animal’s nostrils.

5. Animals with multiple genitals

Some animals own more than one genital. Female marsupials, such as kangaroos, koalas and Tasmanian devils own three vaginas and two uteri, whilst the males have two pronged penises. The two-sided vaginas are used to transport the sperm to their two uteruses, whilst the middle vagina is used for birth. This process allows the females to be constantly pregnant by carrying a baby in their pouch, a foetus developing in one utero and a fertilised egg waiting to be released in the second utero. Marsupials also have the capacity to store sperm for long periods and even delay birth until the pouch becomes free, a great strategy particularly during harsh times of drought and starvation. Due to these reproductive tactics, the population of kangaroos can increase rapidly!!!

Snakes and the lizards are other examples of species carrying multiple genitals. Males own two penises (hemipenes) each one connected to a single testicle and the females have two clitorises (hemiclitoris). Scientists are still unsure why females require two clitorises, but they believe the reason for the two penises is to allow the males to be more flexible and able to mate with the female from either side, particularly during mating aggregations, where as many as 100 males can compete for the same female. Remarkably, female snakes can mate with several males and store their sperm for up to five years and have the capacity to choose which sperm to use to fertilise the eggs.

6. And some without genitals at all

Conversely, there are examples in nature of animals without genitals, such as the squids which lack vaginas. To reproduce, the males store their sperm in enclosed sacs called spermatophores and during mating, they use a special arm to transfer and implant the sacs into the female’s body, generally around her head or near her mouth, where the eggs are waiting to be fertilised. Once fertilised, the female releases the eggs from her mouth or funnel hiding them in the rocks or in holes until they are ready to hatch.

7. Strange Penises

Apart from the kangaroos, snakes and lizards, there are other examples of animals with strange penises. Both ducks and pigs have penis in a shape of a corkscrew or spiral-shaped, which are compatible with a corkscrew-shaped vagina. Boar’s half a meter penis rotates rhythmically during mating and can ejaculate more than half a litter of semen over a period of 15 minutes, whilst duck penises are equally not small, measuring in average about 20cm in length or even half a meter long in the case of the Argentine lake duck. Lucky Donald Duck and Daisy!!

Sea slug’s also use a strange reproductive strategy. They hold three penises and have the capacity to dispose and regenerate one of these penises every time it mates. And scientists seem to know the reason for this perplexing strategy. It appears the sea slugs use their first penis to remove any sperm left inside the female by other males. They then dispose this penis, before using the second penis to inject its own sperm, ensuring that it’s his genes that are passing to the next generation. Miraculously, a few hours later, the male is able to regenerate its first penis and to mate again. Similarly, orb-weaver spiders and other sea creatures also use very similar strategies as the sea slugs.

8. Orphan species

Image from glucosala,
Image from glucosala,

Finally, some animals are orphans from the time they are born. Octopus only go through one single reproductive period and die before their offspring hatch. The males usually die after mating, sometimes killed by the females in an act of cannibalism, whilst the females tend to survive until the eggs are hatched. After fertilization, the female lay the eggs and stand close to them to protect them from intruders, but very soon they stop eating and wastes away starting a process known as programmed death. At later stages some females even go further and start self-mutilation, often slamming against surfaces, tearing off pieces of skin and eating the tips of their own tentacles. By the time the eggs hatch the mother is dead. Scientists are still uncertain why these intelligent animals undergo this process, but it appears it may be an effective strategy to ensure the female does not consume their youngster, particularly since these are remarkable cannibals. Other researchers believe that, since octopus can grow pretty much indefinitely, this may be a strategy to eliminate very big, old and hungry adults that could potential compromise hatchling and to maintain the ecosystem free of massive animals.

Squid use similar strategies during reproduction. Male squid die very soon after mating in order to provide food for the predators that otherwise would feed on the eggs, whilst the female die after releasing the eggs. Similarly, male salmons also die just after spawning but the females survive to guard the eggs, after which they die by exhaustion and the lack of capacity to travel thousands of miles back home to reinitiate their reproductive cycle.

Animals undergo astonish strategies and even ultimate sacrifices, to ensure propagation of their species and generation of viable and healthy offspring. Many more examples exist in nature and these will be part of a future article. Meanwhile, let’s keep observing the world around us and understand the reason behind their complex’s behaviours.  

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the London.

Reference Sources


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2. Kawaguchi M, Okubo R, Harada A, Miyasaka K, Takada K, Hiroi J, Yasumasu S. Morphology of brood pouch formation in the pot-bellied seahorse Hippocampus abdominalis. Zoological Lett. 2017 Oct 17;3:19. doi: 10.1186/s40851-017-0080-9. eCollection 2017.

3. The biology of seahorses: Reproduction. The Seahorse Project.”The biology of seahorses: Reproduction” Retrieved July 2020

Black Widows

4. Welke, Klaas W.; Schneider, Jutta M. (January 2012). “Sexual cannibalism benefits offspring survival”. Animal Behaviour. 83 (1): 201–207. doi:10.1016/j.anbehav.2011.10.027

5. Johnson, J. Chadwick; Trubl, Patricia; Blackmore, Valerie; Miles, Lindsay (August 2011). “Male black widows court well-fed females more than starved females: silken cues indicate sexual cannibalism risk”. Animal Behaviour. 82 (2): 383–390. doi:10.1016/j.anbehav.2011.05.018

6. Baruffaldi, Luciana; Andrade, Maydianne C.B. (April 2015). “Contact pheromones mediate male preference in black-widow spiders: avoidance of hungry sexual cannibals?”. Animal Behaviour. 102: 25–32. doi:10.1016/j.anbehav.2015.01.007

Transsexual Animals

7. Iwata E, Mikami K, Manbo J, Moriya-Ito K, Sasaki H. Social interaction influences blood cortisol values and brain aromatase genes in the protandrous false clown anemonefish, Amphiprion ocellaris. Zoolog Sci. 2012;29(12):849-855. doi:10.2108/zsj.29.849. DOI: 10.2108/zsj.29.849

8. Godwin, J.; Thomas, P. (1993). Sex change and steroid profiles in the protandrous anemonefish Amphiprion melanopus (Pomacentridae, Teleostei). Gen Comp Endocrinol 91: 144-157.

9. Liu H, Todd EV, Lokman PM, Lamm MS, Godwin JR, Gemmell NJ. Sexual plasticity: A fishy tale. Mol Reprod Dev. 2017;84(2):171-194. doi:10.1002/mrd.22691

Camels and Seals

10. Arnautović I.  · Abdel Magid A.M. (1974). Anatomy and mechanism of distension of the dulaa of the one-humped camel. Acta Anat. 115-124

11. Hooded Seal (Cystophora cristata), a weird animal. Retrieved in July 2020.

Kangaroos multiple genitals

12. Ed Yong. Kangaroos have three vaginas. National Geograhic. kangaroos-have-three-vaginas/. April 17, 2012.

13. Marsupial, Wikipedia. Wikipedia foundation. Updated August 2020. Accessed August 2020.

14. Matt Hayes. 10 unexpected examples of animal genitalia. Listverse. 2012

Snakes and Lizards

15. Tina Deines. Why Do Snakes Have Two Penises and Why Are Alligators Always Erect? National Geographic. February, 2018

16. Friesen CR, Uhrig EJ, Squire MK, Mason RT, Brennan PL. Sexual conflict over mating in red-sided garter snakes (Thamnophis sirtalis) as indicated by experimental manipulation of genitalia. Proc Biol Sci. 2013;281(1774):20132694. Published 2013 Nov 13. doi:10.1098/rspb.2013.2694

17. King, RB.; Jadin, R.C.; Grue, M.; Walley, H.D. Behavioural correlates with hemipenis morphology in New World natricine snakes, Biological Journal of the Linnean Society, Volume 98, Issue 1, September 2009, Pages 110–120,


18. Morse P, Huffard CL. Tactical Tentacles: New Insights on the Processes of Sexual Selection Among the Cephalopoda. Front Physiol. 2019;10:1035. Published 2019 Aug 21. doi:10.3389/fphys.2019.01035

19. Pharyngula Friday Cephalopod: Undead Squid Penis. Science Blogs. August 2017

20. Stephanie Watson. How Squid Work. How stuff works.

21. Squid. Wikipedia. Wikipedia Foundation. Last updated 16 August 2020. Accessed September 2020.

Weird Penises

22. McCracken KG, Wilson RE, McCracken PJ, Johnson KP. Sexual selection. Are ducks impressed by drakes’ display?. Nature. 2001;413(6852):128. doi:10.1038/35093160

23. Knox, RV. (2003). The Anatomy & Physiology of Sperm Production in Boars. Published in the internet. Department of Animal Sciences. University of Illinois.

24. Rebecca Morelle. Sea slug’s ‘disposable penis’ surprises. BBC news. BBC. February 2013

25. Ed Yong. Sea Slug Amputates Its Disposable Penis, But Has Two Spares. National Geographic. February 2013

26. Sekizawa Ayami, Seki Satoko, Tokuzato Masakazu, Shiga Sakiko and Nakashima Yasuhiro. 2013. Disposable penis and its replenishment in a simultaneous hermaphrodite Biol. Lett.9. 2012.1150.

Animals who die after giving birth

27. Christina Root. Animals who die giving birth, Accessed September 2020

28. Z. Yan Wang, Clifton W. Ragsdale. Multiple optic gland signaling pathways implicated in octopus maternal behaviors and death. The Journal of Experimental Biology, 2018; jeb.185751 DOI: 10.1242/jeb.185751

29. Matt Wood. The grim, final days of a mother octopus. University of Chicago Medical Center. September 2018.

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The material discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Depression in the Animal Kingdom

Image from blende12,​
Image from blende12,

According to the World Health Organisation, depression is a common mental disorder affecting over 260 million people around the world. It is characterised by a persistent feeling of sadness, lack of pleasure in otherwise rewarding activities, often accompanied with lack of appetite, sleep and concentration and a constant feeling of tiredness. Depression is the result of an imbalance of hormones and chemicals in the brain often occurring during challenging times, but scientists have shown that it also has a genetic component in about 40-50% of the cases.

But, can animals also suffer from this condition? Every so often, animals look lethargic, with an appearance of sadness and lack of interest for activities that they otherwise would enjoy. Can this be the result of alterations on their mental state? If so, what is causing the animals to feel that way and how can help them improve?

By Ricardo Ribas

Whilst animals don’t have the same reasoning capacity as humans and don’t experience the same level of social and psychological complexities, scientists and behaviourists agree that animals can also feel stressed, sad and depressed.

What are the main reasons for depression in animals?

Many factors can trigger alterations in the animal’s mental state. Dogs and cats often develop anxiety and depression as a result of physical illnesses, fears or alterations in the animal’s environment, such as during fluctuations of the owner mood, new pet ownership, relocation to a new home, abandonment or confinement and whilst grieving after a loss of a close human or animal. Despite of being rare in the nature, wild animals can also develop suffer from these conditions, particularly throughout challenging times such changes in the environment, habitat or during death or loss of a close animal.

What are the symptoms in animals?

Researches have shown that mammals, and in particular primates, share anatomic, functional and chemical similarities with human brains, making them the most susceptible species to develop depression. However, since animals are unable to speak and transmit their feelings to humans, makes the diagnosis of these diseases very challenging. To better understand their mental state, scientists base their judgement on the animal’s mood and the changes in their normal behaviour. Primates are perhaps the most transparent of the species and the easiest to illustrate their feelings of sadness based on their facial expressions, but when this not possible, scientists and vets often look for other symptoms, such lethargy, lack of enthusiasm to pleasurable activities, loss of appetite, as well as changes in behaviour and in sleeping patterns. For instance, the majority of the dogs are comfortable when left alone at home for a few hours, whilst others develop obsessive behaviours such as constant barking and crying, repeatedly licking of parts of their body, biting furniture, defecating, urinating or showing changes in their normal behaviour such as aggressiveness, etc. Each animal has its different personality and is very important that the owners understand what is normal or not for each animal. It is also frequent to encounter signs of anxiety and depression in animals kept in captivity, often exhibiting repetitive and compulsory behaviours, such as the constant walking back and forward or in cycles.

Then how can we help the animals through these difficult times?

To start with, it is important to rule out that the changes in the animal’s behaviour are not the result of a simple underlying physical condition or disease. If the animal appears to be suffering from depression-like behaviour, there are a few things the owner can do. Here are some advices:

• Engage with the animal in fun activities, such as games, exercises, etc

• Increase the time spent with the animal and pay more attention to them

• Take your animal for longer walks and exercises

• Incentive the animal to play with other animals

• Limit the time the animal is left alone

• Take time to bond with them

Each animal has a different personality and is essential to understand the reason behind their sadness to better help them. If none of the advices work, consider taking the pet to a behaviourist or to the vet, which can ultimately prescribe antidepressant medications.

Depression can take time but often disappears with some changes in the animal day-to-day life. Nevertheless, it is crucial not to let the disease progress as it can deteriorate the animal’s health and be life threatening.

Large studies are lacking in this field and a lot of research is still necessary to better understand the way the animal feel and how to help them fight the disease. However, many studies agree that animals often help humans improve from depression and that owning a pet can be very beneficial to fight this condition. It is now in our hands to help them too!!

By Ricardo Ribas, veterinary doctor, doctorate in veterinary sciences and scientist in London.

Reference Sources

1. Flint J., Kendler K.S. The genetics of major depression. Neuron. 2014;81:484–503. doi: 10.1016/j.neuron.2014.01.027.

2. Krista Mifflinm. Dogs and Depression. The SprucePets. Updated 28.05.20. Accessed on August 2020.

3. Depression. World Health Organisation

4. Sasha Ingber, Do animals get depressed? National Geographic News, National Geographic. Published 06.10.12. Accessed August 2020

5. Tibi Puiu. Can animals get depressed too? ZME Science. Published 22.09.16. Accessed August 2020.


The material, ideas and prevention measures discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.