Monthly Archives: September 2009

Bat-eating tits!

Posted on by

ResearchBlogging.orgLike pretty much anyone else writing about this, I’m in it for the headline. Well, maybe 30% for the headline — this is also just freaky natural history. A paper in Biology Letters reports that great tits (Parus major — basically big chickadees) will hunt and eat hibernating bats [$-a] if they can’t find other food sources.

The paper reports on ten years of recorded bat-eating by a population of great tits in Hungary, capped by two years of systematic observations and a couple simple experiments. Are the tits hunting bats because other food is scarce? The authors put out birdseed and bacon near the bat cave, and observed that the birds killed many fewer bats. Do the tits use audio cues to find their prey? The authors played a tape recording of bats calling, and watched as the birds oriented to the sound and approached the speaker. There are also a number of grisly photos of tit-killed bats.

This is really the kind of work that attracts most field biologists to science in the first place — a wild, interesting observation that provides an excuse to do some really unusual (and thorough) birdwatching. More complicated science will follow, I hope, like an estimate of the selective advantage this new food source provides to the birds. But it all starts with an incredible story.


You might want to count your fingers after hand-feeding a great tit. Photo by joyrex.

Reference

Estok, P., Zsebok, S., & Siemers, B. (2009). Great tits search for, capture, kill and eat hibernating bats Biology Letters DOI: 10.1098/rsbl.2009.0611

The omnivores’ solution: Tadpoles independently solve a common problem the same way

Posted on by

ResearchBlogging.orgOne of the key observations in support of evolutionary theory is that similar lifestyles can lead distantly-related living things to evolve strikingly similar traits. Compare an echidna and a hedgehog, distantly related mammals with very similar lifestyles. This kind of convergence can occur on much smaller scales of time and space, too, as a new paper just released online by Proceedings of the Royal Society shows. Its authors demonstrate that populations of spadefoot toads have independently evolved the same response to competition from another toad species [$-a].


Spea multiplicata, the New Mexico spadefoot toad. Photo by J.N. Stuart.

As tadpoles, spadefoot toads (Spea multiplicata) have two feeding strategies: they can be omnivores, feeding on organic debris in the water around them; or carnivores, feeding on aquatic crustaceans and sometimes other tadpoles. The two strategies are linked to a developmental switch — tadpoles that start eating crustaceans develop larger heads, the better to eat their fellows, presumably. This switch is handy in minimizing competition for food with another, related toad species, S. bombifrons. In ponds where S. multiplicata and S. bombifrons occur together, S. multiplicata tadpoles are much more likely to become omnivores, and S. bombibfrons are more likely to become carnivores, than is the case for either species when they’re the only ones in the pond.

This solution to competition might have evolved two ways: it may have turned up once, in a single population of S. multiplicata, which was then able to colonize other ponds containing the competitor; or it may have emerged independently in multiple populations experiencing similar natural selection from competition. The new study’s authors show that the second scenario is more likely by comparing the genetic similarity of multiple S. multiplicata populations to the frequency of their competitors, and showing that competition strength, not genetic relatedness, is the better predictor of how likely S. multiplicata tadpoles are to become omnivores.

References

Pfennig, D., & Frankino, W. (1997). Kin-mediated morphogenesis in facultatively cannibalistic tadpoles Evolution, 51 (6) DOI: 10.2307/2411019

Rice, A., Leichty, A., & Pfennig, D. (2009). Parallel evolution and ecological selection: replicated character displacement in spadefoot toads Proc. R. Soc. B DOI: 10.1098/rspb.2009.1337

Crowdsourced dinosaurs

Posted on by

The Open Dinosaur Project opened yesterday, inviting scientists and interested laypersons alike to help assemble a database of published dinosaur skeletal measurements, to serve as the basis for a massive study of evolutionary transitions from bipedality to quadrupedality. Project head (and Open Source Paleontologist) Andy Farke lays it out in an introductory post:

Every step of the way will be blogged. And . . . all contributors are invited to join us as co-authors. The project: look at the evolution of the limbs in ornithischian dinosaurs. [Ellipsis Andy’s.]