The Surprising Friendship of Deer and Bats

The Surprising Friendship of Deer and Bats

post courtesy of project postdoc Dr. Meredith Palmer, who is currently assisting the BBC with a film project in the Serengeti.

Great news, fellow scientists! We’ve just had our first scientific paper from Cedar Creek camera trapping get published in the journal Ethology!

Our research, “Bats join the ranks of oxpeckers and cleaner fish as partners in a pest‐reducing mutualism” pre-dates the Eyes on the Wild camera trapping effort, but reveals the type of exciting new information we can unlock at Cedar Creek. This paper features images from camera traps deployed way back in 2014 by resident ecologist / buildings and grounds supervisor, Jim Krueger.

Jim set out to capture pictures of some of the larger mammals at Cedar Creek, including members of our resident deer population. Now, you can probably tell from the Eyes on the Wild photographs that biting flies are a MAJOR irritant to deer in this ecosystem. You've seen them hovering around our hard-working scientists and interns, as well as on and around many of our wildlife.

These flies plague deer (deer flies are called that for a reason!), opening painful sores and spreading bacterial and viral diseases. There isn’t much that deer can do to get rid of these flies by themselves – but our camera trap footage suggests that deer may be finding help dealing with their infestation from an unlikely friend…!

Over the course of two months, the camera traps captured repeated incidences of a nocturnal association between deer and insectivorous bats. While the hordes of flies make life absolutely miserable for deer, they present a veritable buffet for hungry bats. Bats can easily find all the food they need by hanging out with deer, and, by consuming hundreds to thousands of insects a night, they might provide substantial relief for besieged deer!

Interactions between species where both individuals benefit are known as mutualisms. A classic type of mutualism that you may have heard about from documentaries are ‘cleaning mutualisms’ – think oxpeckers and large mammals, or cleaner fish and their 'clients' on coral reefs. You have one species suffering from detrimental parasites, with the other species removes and consumes. One animal gets de-loused and the other gets a meal! What we see here is almost but not entirely like these kinds of cleaning mutualisms. In the deer-bat interaction, rather than decreasing the abundance of attached parasites, these bats are picking off the flying pests attracted to the deer. There are no reports in the scientific literature on similar interactions: the difference may seem subtle, but this discovery is a whole new kind of positive inter-species dynamic!

It’s also very rare for mammals to be involved in cleaning-style mutualisms, particularly as the partner that does the pest removal. Deer are sometimes the beneficiaries of parasite removal by birds, but bats have never before been recorded to interact in such a beneficial and direct way with other animals! Overall, there has been very little research done on positive inter-species interactions like mutualisms. Scientists tend to focus on predation, competition, and other types of ‘agonistic’ interactions between species in a community, but rarely look for ways that these species help each other out. We use this paper as a call for researchers to report more of these unique kinds of interactions, in the hopes of expanding this field even further.

This important discovery came from just a few months of camera trap data – just think of the amazing things we’ll discover in the photos you’re helping us work through. Be sure to flag interesting or unusual animal behaviors in your pics, and maybe you can be part of writing up your own scientific report! Thanks to all who have continued to tag bats, bugs and other species in the copious pictures of deer on the project - you help us to deepen our understanding of this partnership!

You can read the paper itself on Meredith's blog! The paper was also highlighted on Psychology Today.