Yes, Cold Blooded Creatures Get Fevers Too: Here’s What You Need To Know

What do amphibians, reptiles and fish have in common? They are all ectotherms – cold blooded creatures. They are animals which cannot regulate their own body temperatures (like warm blooded animals can) and they rely on the external environment to change their internal temperatures. 

For long scientists wondered if sickness like cold, flu and fever were the lot of warm blooded creatures . As it turns out – they aren’t. Cold blooded creatures can fall ill too. 

How (?), you may ask. In order to understand this, we need to understand how fevers set in warm blooded creatures. 

All warm blooded creatures have a particular body temperature, which for them is considered normal. For example: 

• Humans – 98.6°F
• Dogs – 102.0°F
• Elephants – 97.7°F
• Horses – 100.4°F
• Goats – 103.4°F

If the body temperatures of these animals rises above this limit (as is the case during infections), the body tries to thermoregulate .i.e. bring the temperature back down, to normal. When the body fails to do this and the body temperature continues to rise, fever sets in. 

 

Cold blooded animals – representative image (Image source: Pixabay)

 

What about cold blooded animals?

Based on this, it’s important to note that for fever to set in, there has to be a biologically-set body temperature. But cold blooded animals don’t have a fixed temperature. Their body temperature falls or rises depending on the temperature of the external environment. 

So, how do they fall ill?

Well, cold blooded or warm blooded, all animals are susceptible to illness. Just as with their warm blooded cousins, cold blooded animals too may get infections from parasites or viruses, which can raise or drop their body temperatures abnormally. Just like warm blooded animals, ectotherm animals’ bodies too can handle only a certain level of heat and cold. If the change in temperature during the infection falls beyond this limit, illness similar to fever sets in. 

But the biggest mystery here isn’t just about how these animals fall ill, but it also includes what these animals do to get back to health. 

Changing behaviours for the sake of wellness

When fish, amphibians or reptiles fall ill, they indulge in what is known as a “behavioural fever“. If the animal is infected by a parasite or virus and experiences signs of ill health, it moves away towards areas which support warmer climates. For example, fish that normally prefer cold waters may swim towards warmer waters when they are ill. 

Why? 

Heat has the ability to deactivate viruses and destroy the proteins which assist in virus duplication. The same goes with parasites – heat can kill them too. 

So, a cold blooded creature that falls ill, will instinctively move towards a warmer place, in order to increase its body temperature, which will in turn help in killing or deactivating the pathogen in their bodies. 

 

Zebrafish (Image source: Imperial College London)

 

This instinctive “behaviour“, which ectotherms exhibit when they have “fevers“, is called “behavioural fever“.  Scientists speculate this behaviour could stem from the fact that the immune systems of cold blooded animals may actually function better when in warmer climates.

One of the best examples of cold blooded creatures who exhibit behavioural fever are Zebrafish. The moment they fall ill, Zebra fish will change their water-heat preferences and swim to warmer waters. The same goes for Guppies. 

When behavioural fever benefits the host 

For some time, it was assumed that behavioural fever was helpful only for ectotherms who were in the throes of infection & fever. But as it turns out, in some cases, the move to hotter areas benefits pathogens too. 

Schistocephalus solidus, a tapeworm found in the gut of  rodents, fish and fish-eating birds, actually thrive on heat. Once the parasite is in the hot climate, it grows stronger and changes the heat preferences of the fish and manipulate other atypical (and often self-destructive) behaviours in the animal. 

 

Virus (Image source: Pixabay)

 

Then there is the Cyprinid herpesvirus 3, which is a virus that attacks fish in the Carp family. This virus affects the genetic code of the fish it infects and overrides the genes which stimulate behavioural fever. So, the infected fish doesn’t move towards warmer waters (as it is supposed to), instead choosing to stay in colder waters, where the virus can gain in strength. 

What happens if a feverish ectotherm cannot move to warmer climates? 

Vicious parasites and mind-control viruses aside, the inability to indulge in behavioural fever can have a massive, negative impact on cold blooded animals. This is in fact, very true of pets.

In the wild, cold blooded creatures have a lot of freedom to move to different places, in order to rid themselves of their illness and infection.  But pets stuck in aquariums and enclosures don’t have this luxury. 

Cold blooded pets like fish, turtles, tortoises, iguanas, lizards and snakes are cooped up inside their temperature-controlled tanks/enclosures for almost their entire lives; where they are subjected to the same temperature day-in-and-day-out. 

 

Caged animal – representative image (Image source: Pixabay)

 

Now imagine these pets fall ill and have a fever. Biologically they are programmed to leave and move to a place that is warmer, to heal themselves. But because they are stuck in their tanks/enclosures, these animals do not get the opportunity to get their bodies at the right temperature to kill the infection. 

When this happens, the fever and the infection only gets worse and in the worst cases, the pet dies. In fact, a large number of fish deaths in aquariums can be attributed to this.

So, what can pet owners do about this? 

Fish owners can set aside a separate tank where they can change the temperature of the water as required. Owners of amphibians and reptiles can create heat spots in corners of the enclosure by using detachable heaters and small light sources. This can give the sick pet an opportunity to self-heal. 

If however, your pet looks worse, it’s best to take him/her to a vet immediately. 

 

 

-NISHA PRAKASH 

P.S: Featured image: Iguana (Source: Pixabay)

5 Fun Facts About Africa’s Great Migration

You may have seen it on television – it’s an event that National Geographic has always loved to film. A grand spectacle and a treat for the senses, the Great Migration in Africa is the annual movement of the world’s largest (non-human) land animal group from one part of Africa to the other, in search of food and safer breeding grounds*.

Wildebeests, antelope, zebra and big cats congregate for five months of rigorous walking, eating, birthing and killing. Here are 5 amazing facts about it:

1. The Great Migration starts in Tanzania at the Serengeti and Ngorongoro Conservation areas and ends at the Maasai Mara National Reserve in Kenya. The migration starts in the month of November and the animals reach their destination in March.
2. A recorded 1.5 million wildebeest, 200,000 zebra and thousands of antelope make the migration each year. The animals travel a staggering 2900 kilometres (1800 miles) in total, from Tanzania to Kenya and back during this journey.
3. The Great Migration follows one of the most dangerous routes in Africa. Animals making the journey have to deal with hungry predators (lions, cheetahs & crocodiles), treacherous floods, the uncaring African sun, mean-spirited tsetse flies and physical tiredness. More than 250,000 wildebeests and thousands of zebras and antelopes die each year on the journey. This is excluding the thousands of calves who are left orphaned and vulnerable to predators after their mothers die. A recorded 3000 lions follow the herds on their journey, picking off the weak and the injured.
4. More than a foraging mission, the Great Migration is a breeding expedition. Pregnant wildebeests move from Tanzania to Kenya for better environmental conditions for calving. An estimated half a million baby wildebeests are born annually during the migration. In the peak of the calving season (February), more than 8000 wildebeest calves are born in a single day!
5. Although they look like they’re confused and panicked all the time, the massive herds of wildebeests, zebras and antelopes actually function together as one cohesive unit. They display a tactic researchers call “swarm intelligence”, where they carefully analyse, strategise and implement a  plan of action to get safely past any threat together. There’s no “I” in this family.

 

Bonus

There is still no established and accepted explanation for the occurrence of the Great Migration.

Some scientists believe the changing chemistry of the grass could be the reason for the movement. When levels of phosphorous and nitrogen in the Serengeti grassland reduces, the wildebeests may be encouraged to move elsewhere for more nutritious meals, acting as the catalyst for the Great Migration. Others believe that the migration may be the result of a co-ordinated effort helmed by a leader. But so far there has been no evidence of there ever being an alpha-wildebeest in any herd. Then there are those scientists who believe that the Great Migration is the consequence of instinct and DNA – a purely biological process that has no other reason.

Well, whatever the rationale, fossil records show that the Great Migration has been in occurrence in East Africa for over one million years.

 

The Great Migration – Route Map (image source)

 

A sea of wildebeests, zebras and antelopes greet the eyes during the Great Migration. Often, these herds extend all the way to the horizon; but they don’t stop there. They go on & on. (image source)

 

Wildebeests crossing the Mara river – this is where they are most vulnerable to attack from crocodiles. (image source)

 

A wildebeest mother with her newborn calf. (image source)

 

Video: Watch the culmination of the Great Migration – wildebeest giving birth & a newborn’s first, wobbly steps. 

 

-NISHA PRAKASH

P.S: Featured image

*Humans take the crown for the farthest migrations in search of food and shelter.