The challenge of being small - alternative wintering strategies in high-metabolic non-hibernating terrestrial mammals
Red-toothed shrews (Sorex spp.) are excellent model organisms to study the evolution of brain size under energetic limitations. Previous work suggests that several Sorex spp seasonally shrink and then regrow of the brain, parts of the skeleton, and brain case. PhD student Javier Lazaro looks at the causes and consequences of this amazing phenomenon both in the field experimentally. This is a collaboration with the MPG-Poland Biodiversity Initiative, in close collaboration with Jan Taylor at his field station in Poland, Chet Sherwood and Moritz Hertel.
We have been putting a lot of effort into studying the energetics and food use of these shrews as they go through the stages of this phenomenon. Our friend and collaborator Paul Schaeffer has been crucial here and we are just starting to dig into the data we collected together with bachelor student Japhet Breiholz on their metabolism and by master student Lara Keicher in collaboration with Christian Voigt from the IZW Berlin on food incorporation and fat turnover.
The smallest Mustelids (e.g. Mustela nivalis) share several similarities with Sorex species, including an elongated body shape, predatory behavior, and a high metabolic rate. Former Postdoc Scott LaPoint now showed that M. nivalis also exhibits Dehnel’s Phenomenon. This widened taxonomic scope is, of course, extremely relevant for the understanding of the evolution of this phenomenon and increase the promise of potential applied research using animals that exhibit Dehnel's Phenomenon. Scott collected a suite of braincase size metrics on museum specimens and quantified the season variation in the skulls of these weasels after controlling for other variables such as latitude, elevation, sex, and age, which mask the pattern of the Phenomenon. Excited to have discovered seasonal skull and brain size changes in the weasel, as well as anecdotally in more species (mink, polecat, mole), we are collaborating with Karol Zub and Sharon Swartz among others, to address questions that may not be possible to investigate in the tiny and stress sensitive shrews
Combining all of the interests outlined in our other projects we also study the evolution of brain size from a phylogenetically comparative angle. Using published data, topped up by data we collect ourselves, employing phylogenetically-corrected methods we explore how tightly adapted bats are to their ecological niche. With Kamran Safi and Jeroen Smaers we are interested to understand the patterns of evolution that led to the species populating our planet today. But we also study how adult neurogenesis may function to modify the adult olfactory brain in bats and how this may be linked to the ecology and social environment of bats in collaboration with Liliana Davalos.