Octopus of Many Talents

“So! I was wondering if you knew anything about the Indonesian Mimic Octopus. Apparently it can mimic 15+ different species like the lion fish or a flounder for defensive purposes, but I was wondering if it would have to observe these animals to mimic them or if its an instinctive evolutionary trait, or if it’s even known. I tried looking for resources but couldn’t find anything definitive. I know octopuses are a far cry from birds but I thought it was cool and was wondering if you knew any more”

— Anonymous

I couldn’t find anything directly relating to this either, unfortunately! According to the original paper of the description of the species, it was hypothesized that the ability to mimic certain shapes was genetic, but when to use each posture was a direct reaction to the current environment.

For example, the octopus would only use the posture resembling a highly venomous sea snake when faced with territorial damselfish - because the damselfish are commonly predated by that specific sea snake. 

Photo from NCBI

It really isn’t that different from other cephalopods and their crypsis - most octopuses mimic surroundings, in terms of changing skin colour, texture, and form - so there is a genetic basis for it. The mimic octopus lives in a predator-heavy, open habitat, however, so there was likely strong selective pressure for an alternative to hiding as rocks or coral. Those who managed to resemble local venomous species were likely way more effective than those who didn’t.

They’re pretty cool though, and if anyone else knows more about them, I’d love to hear it!

Alligator Engineers

“Q: So what’s the point of a crocodile/gator? What contribution do they bring to the food chain? and such?”

— Anonymous

You mean besides just being freaking adorable dorks all the time????

Photo from Clayton Bownds

Well my friend, I hope you are prepared for the long-winded summary on predator-prey population dynamics that you have unleashed here.

As a general rule, any apex predator is crucial to an ecosystem, specifically because they regulate population numbers of their prey species and leave remains that can be exploited by smaller animals. Crocodilians are typically the largest freshwater predator in their ranges, and due to their ambush hunting method and amphibious* lifestyle, they have a huge range of prey species. They will eat anything they can catch, of any size, including fish, amphibians, other reptiles, both large and small mammals, birds, people - the list goes on and on. But let’s get a bit more specific.

Alligators (both American and Chinese) are allogenic ecosystem engineers, meaning that - like beavers, caterpillars and woodpeckers** - alligators physically change their environment and, as a result, change the resource availability in those areas. Adult alligators will dig and expand “gator holes” that stay filled with water even during droughts, allowing tons of other species to survive dry periods.

Photo from EarthSky

On top of that, American alligators are currently the only predator large enough to make a dent in the invasive Burmese python population that is literally destroying the Everglades as we speak. Unfortunately, the predation goes both ways.

Photo from Reptipedia

Crocodiles are a bit tougher to describe, mostly because there are a whole pile of species, but all are important in prey population control and particularly in scavenging carcasses. Crocodiles have the strongest stomach acid of any vertebrate, and as such can eat just about anything, including rotting carcasses that would otherwise pollute water systems. 

I’m not going to go into all of the species of crocodile, because it would take several weeks, but I will say that the saltwater crocodile is pretty neat - not only as the largest crocodilian, and the one with the largest range of prey species - but because it is currently the only predator in Australia that has been shown to be able to survive eating the highly toxic and invasive cane toad***. 

Even though you didn’t ask, I’m gonna just touch on the two other types of crocodilians, because I love them. Gharials are highly specialized crocodilians that would normally regulate fish populations - if they weren’t critically endangered - and caimans are smaller, highly adaptable crocodilians. Cuvier’s dwarf caiman in particular is a keystone species.

A couple other things about crocodilians to chew on:

• Crocodilian meat and leather is a HUGE market, and is fueling conservation and breeding efforts that might otherwise not be there

• Crocodilians are a very effective tourist draw (read: more conservation)

• Abandoned nests turn into peat, also important for wetland ecosystems

• Crocodile tears are a real thing but most likely not due to emotion

TL;DR: CROCODILIANS ARE SUPER IMPORTANT, MAINLY BECAUSE THEY EAT STUFF

*Except gharials. As a rule, gharials look pretty dorky on land.

**Humans are also technically in this grouping, but I didn’t want to insult alligators with the comparison.

***Not proven as a possible population control, however. Too bad.

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SOURCES YO

http://crocodilian.com/cnhc/csp_amis.htm

http://science.time.com/2012/01/31/invaders-how-burmese-pythons-are-devouring-the-everglades/

http://www.fws.gov/endangered/esa-library/pdf/alligator.pdf

https://www.ehp.qld.gov.au/wildlife/livingwith/crocodiles/

Toxic tucker: the potential impact of Cane Toads on Australian reptiles

http://animaldiversity.org/accounts/Gavialis_gangeticus/

http://infochangeindia.org/environment/politics-of-biodiversity/a-hundred-dead-gharials-and-the-gaia-effect.html