All Creatures Great and Small: Small Mammals and Conservation Paleobiology

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Small mammals, at times, don’t seem very interesting or informative (like when there is a rat in your apartment and you just want it out.) A lot of paleontologists are keen on studying enormous carnivorous beasts like dinosaurs and sabre-toothed cats and are not often thinking about small, adorable (at least I think so) rodents. Fortunately for us, some people love all creatures, great and small. Ancient and modern small mammal communities are probably the best indicators of how  climate change will affect diversity, extinction, and speciation of vertebrates as a whole. They are often the base of food webs and vital to the survival of ecosystems. We were recently discussing how paleontology is relevant, and I would say these fossils are some of the most important resources we have as paleontologists interested in researching the future of global biodiversity in the face of warming temperatures.

A paper I read recently by Prost et al. 2013 in Global Change Biology serves as an excellent reminder of the dangers facing small mammal communities in a warming world. They utilized both ancient and modern data to help understand the future of both the narrow-skulled vole and collared lemmings. Polar regions are particularly interesting to study because they exceed tropical and temperate regions in warming. They used both ancient DNA and ecological niche modeling to look at changes in populations and biogeography since the Last Glacial Maximum, and then used this information to project into the future potential issue these vital species may have.

A friendly vole (Wikimedia Commons)

Interestingly, while both are small mammals that superficially occupy similar niches, they responded differently after the Last Glacial Maximum. The collared-lemming had a distinct range decrease, while the narrow-skulled voles were only minimally impacted. Also fascinating is that there is a strong correlation between extent of suitable habitat for narrow-skulled voles and their ancient genetic diversity. These animals are at the bottom of the food chain, and their survival can be integral to the entire artic and boreal forest ecosystem.

Population sizes in the two species (collared lemming in green, narrow-skulled vole in purple, oxygen isotope values  of ice core on the bottom) reacted differently after last glacial maximum. Collared lemmings clearly had a more severe population decrease than narrow-skulled voles. (Figure 2, Prost et al. 2013).

Population sizes in the two species (collared lemming in green, narrow-skulled vole in purple, oxygen isotope values of ice core on the bottom) reacted differently after last glacial maximum. Collared lemmings clearly had a more severe population decrease than narrow-skulled voles.       (Figure 2, Prost et al. 2013).

Another researcher who does stellar work on climate change and small mammal communities is Rebecca Terry. I greatly admire the importance and interdisciplinary nature of her modern and paleo-ecological work. The bulk of her work to this point has been analyzing small mammal bones in caves form the Great Basin region of the western United States. In a 2011 paper, Terry et al. analyze cave data from the last 7500 years to see how this rodent community responded to past climate change. The skeletal remains in these caves are predator-derived, meaning they are mostly owl and raptor regurgitate (pellets). These preserve the hard parts from prey and represent a solid composite signal of long term demographic trends.

Owl pellets contain bone and hair from prey (Wikimedia Commons)

The results clearly indicate a rather unexpected trend.  Rodents with diets adapted to plant fodder had a marked decline during dry periods, while rodents that primarily ate seeds dominated the faunal assemblage. Climate models show the Great Basin will warm considerably over the coming decades, so this sort of detailed information obtained from paleocommunities can help us conserve populations that are apparently vulnerable to these climate shifts.

I think these types of studies are so important to point out because they illustrate that our fossil record can be robust and useful for conservation- this has brought about the relatively new subfield ‘conservation paleobiology’ where we use paleo-information to inform modern conservation. Most of these studies are also quite interdisciplinary, using ancient DNA, niche modeling, stable isotope sampling, etc. Robust, all-inclusive sampling is needed to best understand the information locked in these fossils. Although big dinosaur fossils are cool, those finds are often sparse, and can’t tell us the useful, nitty-gritty details of community response to climate change.

Let this be a lesson to you future paleontologists, don’t ignore the little guys!

 

References:

Prost, S., Guralnick, R. P., Waltari, E., Fedorov, V. B., Kuzmina, E., Smirnov, N., van Kolfschoten, T., Hofreiter, M. and Vrieling, K. (2013), Losing ground: past history and future fate of Arctic small mammals in a changing climate. Global Change Biology. doi: 10.1111/gcb.12157

Terry, R. C., Li, C. and Hadly, E. A. (2011), Predicting small-mammal responses to climatic warming: autecology, geographic range, and the Holocene fossil record. Global Change Biology, 17: 3019–3034. doi: 10.1111/j.1365-2486.2011.02438.x

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