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Are crocodiles secret fruit-lovers?

Seed dispersal by animals is important for plants to help them occupy new areas of land. Usually bugs, birds, or intrepid kittens do that job. Now we can add crocodiles to that list. A new study reviewed…

Five-a-day please. blacktigersdream

Seed dispersal by animals is important for plants to help them occupy new areas of land. Usually bugs, birds, or intrepid kittens do that job. Now we can add crocodiles to that list. A new study reviewed the diets of crocodiles and showed that 13 of 18 species ate fruit of some sort and a wide variety of plants.

Using animals as a method of seed dispersal is actually a useful form of mutualism – the plants get to spread their genes and animals get a healthy snack. In other reptiles seed dispersal is a well-known activity, although not as well understood as for insects, mammals, birds and even in snakes.

The recent study, published in the Journal of Zoology, shows that for crocodiles, almost a quarter of the fruits consumed were of the “fleshy” kind. However, none of the recordings were of direct observations of fruit eating, so exactly how or why they did is still a bit of a mystery.

Most of the evidence come from dissection of crocodiles' stomachs and their faeces. So there is some chance that these crocodiles are indirect eaters of fruit who feast on fruit-eating animals. But direct observations (see video) have been made many times to believe that they might actually like eating fruits.

Why do it? First researchers that crocodiles learnt this behaviour from alligators in captivity. But the review makes note of observations in the wild. Perhaps it is similar to why dinosaurs consumed stones (gastroliths), to help with grinding food in their stomachs and get a tasty treat in the process. The energy values of fruits are pretty high, so consumption could be for a nutritional benefit.

Perhaps this odd phenomenon might help in part explain why crocodiles are such successful animals. If meat was ever in short supply, they had the capacity to diversify and track down other food sources, from vegetation and grasses.

The study reveals something interesting about the way scientists might operate. Crocodiles are obligate carnivores – their primary diet is meat – and as such, fruits are often classed as anomalous food items when found in their stomach and not considered in a physiological context. This mainstream view may have led to the ignorance that feeding on fruits could help their diet and energy balances.

That the review study picked up so many independent instances of crocodiles feeding on fruit and having ingested seeds is solid evidence for this. It shows that sometimes stepping back and taking a broad look at evidence can reveal some interesting things.

This is an edited version of a post that appeared on Jon Tennant’s blog.

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  1. John Stell

    logged in via Facebook

    "scientists interpret nature through a lens: the meat in a crocodile’s diet is “obligate,” but the fruit is an “anomaly.” Could that be backward?"

    That is not my question but it is a good one, considering that it appears the very idea that crocs even eat fruit is some kind of new discovery. I'm guessing there is very little study of their feeding in the wild, someplace where both fruit and meat are plentiful, or various circumstances. Perhaps there would be more 'suprises'?

    I took the question from the following article, I suggest it for your consideration (as open minded investigators seeking the truth wherever it leads):

    1. Jon Tennant

      PhD student at Imperial College London

      In reply to John Stell

      Hi John,

      I don't think it is backward. The point of my article is that it is found in many independent cases, but never synthesised into an analysis, as was done in the initial study (I think it's behind a paywall, but I can send you a pdf!) It certainly doesn't imply in any sense that crocodiles are obligate frugivores who like the occasional steak - everything in their digestive and ingestive physiologies goes against this (why be such an efficient hunter if you're designed to eat fruit?) But it does show that there is an additional vein of complexity to the feeding habits of archosaurs. Cheers for the post! :)