Tetrapod Zoology

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A few years ago Brito et al. (2002) published a brief but very interesting little paper in which they reported frugivory in Broad-snouted caimans Caiman latirostris. Two captive Brazilian animals were observed and photographed feeding on the fruit of Philodendron selloum [photo here is Fig. 1 from Brito et al. (2002)]. They later offered fruit to the caimans again “and frugivory was confirmed with other caimans from the pen” (p. 96: the ambiguous wording indicates that other individuals were happy to accept and eat the fruit as well). Apparently, herbivory has been recorded on quite a few occasions in crocodilians, but the general feeling is that such acts were accidental, with the animals presumably ingesting bits of plants when grabbing at animal prey. New observations imply, however, that herbivory might be far more widespread, and perhaps more important, in crocodilians than thought.

As reported on the St. Augustine Alligator Farm Zoological Park website, captive American alligators Alligator mississippiensis were observed eating from elderberry plants in 2000, and were definitely eating plant material (rather than grabbing at small animals lurking in the foliage). Alligators at the park have also been seen to eat lettuce leaves and squashes from bowls put out for tortoises, and this behaviour was commonplace enough for it to be filmed. Some of the alligators have been observed eating kumquats, oranges, lemons and limes. The video sequence included here shows an American alligator eating kumquats. Honest.

What gives? Do these observations indicate that extant crocodilians are not strict carnivores, and that fruits and even leaves are a normal supplement to their diet? We don’t know, field observations are needed. There is another, equally interesting possibility however: this being that the captive animals that we’ve been looking at have been mimicking other species. At least some of the alligators at the St. Augustine Alligator Farm Zoological Park are kept with tortoises, and have been eating the food put out for the tortoises. And as for the fruit-eating Brazilian caimans, Brito et al. (2002) drew attention to the fact that they were kept together with tegus Tupinambis merianae, and tegus are well known for eating fruit. Might the caimans therefore have seen the tegus eating fruit, and therefore “acquired frugivory behaviour from the tegus” (Brito et al. 2002, p. 96)); or, in other words, copied them.

It seems to me to be quite a sophisticated thing for an individual of species 1 to watch a member of species 2 perform an act that is alien to species 1 and to then mimic it, but evidence indicates that crocodilians really are quite sophisticated creatures, and probably smarter than is generally realised. Eating fruit when you have a skull and dentition suited for eating meat is – it seems – not difficult, and in fact carnivores may make the transition to some kinds of herbivory quite easily. Examples among mammals include red pandas, and procyonids like kinkajous. Among reptiles there’s the herbivorous raptor, Gypohierax angolensis, the Palm-nut vulture. We await more data on this very interesting subject.

Thanks to Tim Isles for heads-up on the St. Augustine website.

Refs – -

Brito, S. P., Andrade, D. V., & Abe, A. S. (2002). Do caimans eat fruit? Herpetological Natural History, 9, 95-96

Comments

#1 Jerzy
October 3, 2008

I had a water turtle which was intensively curious about everything in and around his terrarium. BTW, even fish are, if you wave something shiny in front of aquarium.

However, the turtle generally, satisfied its curiosity by 1)looking, 2)smelling 3)biting the item. If thing was small and chewable, it was eaten. If it was inedible, it was still chewed from time to time, just in case it transmuted. So I observed lithovory, dactylovory, herbivory, stickovory, aquafilterovory, paperovory, glassovory, cleaningnetovory, and spongeovory. Maybe it is indication of intelligence?
#2 Dartian
October 3, 2008

Learned frugivory by crocodilians would be quite amazing if true. But is it not possible that this could be some kind of displacement activity, caused by (for example) boredom in captivity, rather than serious feeding behaviour?

It’s true, though, that there are some surprising frugivores out there. At least one species of frog eats fruit (da Silva et al., 1989), and I don’t think there is any reason to believe that these frogs are copying the behaviour of some sympatric non-anuran frugivore.

Reference:

da Silva, H.R., de Britto-Pereira, M.C. & Caramaschi, U. 1989. Frugivory and seed dispersal by Hyla truncata, a Neotropical treefrog. Copeia 1989, 781-783.
#3 Sordes
October 3, 2008

Very interesting topic. This makes it much easier to understand how creatures like Chimaerasuchus could have evolved, because crocodylians seems really to be the very last ones which would accept plants in their diet. Really cool. This reminds me on another very strange animal behavior. Mantids are among the most formidable predators in the insect kingdom and known for their massive appetite for meat. There was even at least one case of massive auticanibalism in which a mantid ate both of its arms after it accidently did bite in them.
But the really strange thing is that this insects seems to accept bananas as food too and can even live from this fruits.
#4 Dartian
October 3, 2008

By the way, I would have expected any self-respecting caimans to eat the tegus rather than the fruit…
#5 Sigmund
October 3, 2008

Are bananas the alligators nightmare?
#6 Christophe Thill
October 3, 2008

Do you think the alligators will learn to wash the fruit before eating?

By the way, what’s a Philodendron fruit like? Is it any good?
#7 Felicia Gilljam
October 3, 2008

Do wolves eat fruit in the wild? Both dogs and cats seem to have a bit of a sweet tooth after all.
#8 Jerzy
October 3, 2008

BTW, palm-nut vulture is really unusual specialization which strangely doesn’t attract researchers. I saw several in zoos, but read nothing about them.
#9 David Marjanovi?
October 3, 2008

Cats don’t have a sweet tooth. They can’t even taste sweet — their gene for the sweet-receptor is broken.

Sure, tigers eat durian, but for other reasons.
#10 Dartian
October 3, 2008

Jerzy:

palm-nut vulture is really unusual specialization which strangely doesn’t attract researchers.

Maybe not attraction from researchers, but I’ve seen creationists use the palm-nut vulture’s dietary habits as ‘evidence’ for their idea that all animals, including raptors, were vegetarians in the Garden of Eden.

And Tyrannosaurus‘ teeth were just perfect to open coconuts with, didn’t you know?
#11 Tengu
October 3, 2008

I have observed dogs delicatley pull blackberriess off low hanging bunches, so I assume they like them.

Dogs will eat anything swallowable, so this tells us very little.

My friends have been comparing frightening lists of things their pest has eaten, often very expensive ones.
#12 Sam C
October 3, 2008

Frugivory?? Surely fructivory? Or has Latin changed since I digested it in the 1970s?
#13 Warren B.
October 3, 2008

‘Course, the best-educated among us already know that the peach assailant should be attacked with a crocodile.

This post vaguely reminded me of something called alligator apples. Wikipedia assures me I wasn’t hallucinating. Also, another arthropodal anecdote involves captive theraphosids accepting frozen peas, in a report from the JBTS. (Volume 8, No. 1, 1992; though I was sure there was another)
#14 neil
October 3, 2008

Awesome post Darren! This is a perfect corollary to frog eating dukiers, flesh-crazed hippos etc. Perhaps you can take up the “rogue walrus” phenomenon some time? As someone who (ostensibly) studies feeding behavior in extinct animals, this kind thing makes me lay awake at night in a cold sweat.

Regarding frugivory in wolves, most wild canids consume a fair amount of plant matter including Canis lupus. This is not simply a lack discretion–canids make a habit of exploiting seasonal fruit. This time of year in California, it’s almost impossible to find a coyote scat that is NOT packed with manzanita berries. Maned wolves depend on fruit for up to half of their diet by volume, perhaps others are even more frugivorous?
#15 Darren Naish
October 3, 2008

Thanks Neil. I just read Delfino et al.’s new paper on Acynodon and was pleased to see some discussion of alligatoroid herbivory therein: the weird dentitions of a few Cretaceous eusuchians have resulted in speculations on plant-clipping. Langston suggested, incidentally, that nettosuchids (which are now thought to be gigantic duck-billed caimans) might have eaten algae and other floating plants.

As for walruses, there are some neat photos of big adult males tearing baby ringed seals to pieces, and I would like to cover this. There is probably enough stuff to do on walruses for a whole week of posts. Hmmm…
#16 Webs
October 3, 2008

I’m surprised I haven’t yet seen a mention of therizinosaurs or prosauropods.
#17 Zach Miller
October 3, 2008

Ya’know, speaking of Chimaerasuchus, I’ve been looking for its description…*wink wink nudge nudge*

My leopard geckos will eat anything that enters their tank, although I doubt this is a sign of intelligence. Various objects have been bitten over the lives of my four lizards, including (but not limited to) fingers, toys, the poop scooper, each-other, water spritzer’s tube, and foliage.

Upon clamping down, the lizard would hang on for several seconds, weighing the pros and cons of going to the effort actually swallowing. The thought process seems to be this: If it’s bigger than my head, it’s not edible. Thus, the lizard releases his iron grip. Leopard geckos have surprisingly strong bites, strong enough that I’m leery of feeding them all at the same time, because they’ll bite each-other in the Quest for Mealworms.

Herbivory in ‘gators is awesome news. Makes me wonder if they would go the way of that…that one lizard…you know…that evolved herbivory in like 36 years (recently) if a group of ‘gators was stuck on an island.
#18 Will Snyder
October 3, 2008

So does this occasional omnivory/frugivory in alligators allow for the possibility of herbivorous frugators, or would the specialization in predation continue to dominate their lifestyle? As a ‘speculative biologist’, I’m intrigued to see the possibilities to specialize such a strange behavior (especially since this specific behavior was in fact the lifestyle of at least a few prehistoric crocodilians).
#19 John Brueggen
October 3, 2008

HI,I’m glad you found my paper and video about omnivorous crocodilians. There are many other people that have shared their similar experiences with us since I published the paper. It happens with alligators and caiman that are not housed with other fruit-eating reptiles as well.

John Brueggen
Director
St. Augustine Alligator Farm Zoological Park
#20 John Brueggen
October 3, 2008

By the way I published my paper in the Proceedings of the 16th Working Meeting of the Crocodile Specialist Group in October of 2002.

Also, other papers you might find interesting:

BLOHM, T. 1982. Husbandry of Orinoco crocodiles (Crocodylus intermedius) in Venezuela. Pp. 267-285
in Crocodiles. Proceedings of the 5th Working Meeting of the Crocodile Specialist Group, IUCN � The
World Conservation Union, Gland, Switzerland. ISBN 2-8032-209-X. 409 pp. (Orinoco adult feeding
Young)

CARPENTER, C.D.H. 1928. Can Crocodiles swallow their food under water? Nature (Lond.) 122:15
#21 William Miller
October 3, 2008

That’s … really bizarre. And interesting. And bizarre.

Thanks for another cool, informative post!
#22 Dr. Nick
October 4, 2008

From Sam C:

Frugivory?? Surely fructivory? Or has Latin changed since I digested it in the 1970s?

Nope. fru^x, fru^g- ‘fruit’ (though apparently fru^x was used more for things like beans and lentils, and fru^ctus more for tree fruit).
#23 Bill Parker
October 4, 2008

I just made the mistake earlier this week of introducing my dog to cherry tomatoes. First, I threw her an overripe one and she picked it up and spat it out, tried several times more and just would not consume it. However, this was after a regular meal. A few days later I threw her another tomato (assuming she would not eat it) BEFORE her meal and she spat it out at first but then consumed it. Now she is starting to actively forage for them in my garden.
#24 carel
October 4, 2008

Swallow-tailed Kites (Elanoides forficatus) have been recorded eating the fruits of Rubber and Matayba Trees (Condor 81:207-208) in the wild.
#25 Jura
October 4, 2008

Varanus olivaceous is another well known fruit eater that has evolved from a “traditionally” carnivorous genus.
#26 Hai~Ren
October 4, 2008

Wow, this was certainly a big surprise for me, though on hindsight, I guess it really just goes to show that there’s always something new to learn, even for species which are supposedly very well-studied.

I guess many carnivores might be able to perceive the nutritional value in certain fruits. It would certainly be more interesting if they started deliberately munching on leaves.

What next, snakes swallowing tubers? Sharks eating kelp?
#27 Felicia Gilljam
October 4, 2008

David M, Of course you’re right. What I meant to say is that at least some cats are known to eat fruit occasionally.

Whomever said dogs will eat anything swallowable isn’t correct. My dog showed clear preference for sweet vegetables and fruits. She wouldn’t eat salad or onion, cucumber was alright but red peppers and any sweet fruit was the preference. She’d also happily eat blueberries (out in the woods, without us feeding her) but avoid lingonberries. Which makes me wonder if wolves have been seen to do the same.
#28 Bee
October 4, 2008

Omnivorous behaviours are observed from the other direction as well. White-tailed deer have been observed eating nests complete with nestlings, and even eating birds caught in mist-nets (there’s a paper on this which I’ve read, but can’t find now, of course). Red deer in Scotland were observed to prey on Shearwater chicks, though in that case they were eating heads, legs, wingbones, possibly in search of minerals. There are also stories of deer eating fish and squirrels.

My dog was also an enthusuastic blueberry picker, a pain to take berry picking, because as soon as I’d settle into a good patch, she would rush over to take advantage, raking the berries off the branches with closed teeth and lips.
#29 sinuous_tanystropheus
October 4, 2008

Felicia-

I didn’t know this until recently either, but they say it’s bad to feed dogs onions. Same with some others I didn’t know about like garlic, grapes, and macadamia nuts. Chocolate too (although most people know chocolate’s bad). I don’t know the details on why but I expect it would be easy to google for them.
#30 Alan
October 4, 2008

Fascinating. How does this impact the interpretation of the mekosuchine crocodiles you wrote about in v1? I would think an isotopic analysis of the bones might show if they incorporated a percenatage of vegetation in their diet. The short snouts of the forms you illustrated remind me a bit of Blue Tongued skinks Tiliqua, which are omnivorous feeders.
#31 anthropopotame
October 4, 2008

There is a Brazilian study (unfortunately I don’t remember the reference here) that shows that black caiman (melanosuchus niger) and other caimans feed almost only on fruits during rainy season in the Amazon basin, when the fishes are scattered in the varzeas. So it looks like it is really a typical behavior…
#32 David Marjanovi?
October 5, 2008

Chocolate too (although most people know chocolate’s bad).

Not for the teeth, though; the theobromine prevents caries. Seriously.
#33 Monado
October 5, 2008

What about this “lizard develops herbivory in 36 years”? Reference, please!
#34 Sven DiMilo
October 5, 2008

lizard evolves herbivory in 36 years:
http://www.pnas.org/content/105/12/4792.full.pdf
#35 Sordes
October 5, 2008

I don�t know about any shark which eats plant-material (only the kelp-eating species shown in a Simpsons-Episode), but it is well known that many south-american freshwater stingrays consume plant materail. It is unprobable that this is only accidental, and they even eat cucumber in aquariums.
#36 Christina Crosby
February 24, 2009

Frogs eating strawberries!!! Well its true and we were plagued with them. Of course no one believes my husband and I- but despite netting against birds the common English Garden frogs that proliferate in my garden took to taking chunks out of our strawberries. Because they did not eat them whole fruit we assumed initially that it was slugs or toothless mice as the whole fuit was somewhat squashed. Anyway, over days there was never a frog free day- however I don’t think it was good for them as they became extremely bloated. Anyone else experienced this?
#37 joel hanes
May 9, 2010

Coyotes eat windfall avocados.
#38 Terry
February 26, 2011

I would like to know if Gators have ever been observed eating tomatoes(?).Or, “Do Gators eat maters?”
#39 Nathan Hofstad
February 27, 2011

Well, this is rather mind-blowing to discover, to say the least. I know that coyotes will eat avacados and other fruit crops, and that the Gray’s monitor feeds on fruit, but never would’ve expected it of gators. Huh.