Life history and habitat do not mediate temporal changes in body size due to climate warming in rodents

Abstract

Temporal changes in body size have been documented in a number of vertebrate species, with different contested drivers being suggested to explain these changes. Among these are climate warming, resource availability, competition, predation risk, human population density, island effects and others. Both life history traits (intrinsic factors such as lifespan and reproductive rate) and habitat (extrinsic factors such as vegetation type, latitude and elevation) are expected to mediate the existence of a significant temporal response of body size to climate warming but neither have been widely investigated. Using examples of rodents, we predicted that both life history traits and habitat might explain the probability of temporal response using two tests of this hypothesis. Firstly, taking advantage of new data from museum collections spanning the last 106 years, we investigated geographical and temporal variation in cranial size (a proxy for body size) in six African rodent species of two murid subfamilies (Murinae and Gerbillinae) of varying life history, degree of commensality, range size, and habitat. Two species, the commensal Mastomys natalensis, and the non-commensal Otomys unisulcatus showed significant temporal changes in body size, with the former increasing and the latter decreasing, in relation with climate warming. Commensalism could explain the increase in size with time due to steadily increasing food availability through increased agricultural production. Apart from this, we found no general life history or habitat predictors of a temporal response in African rodents. Secondly, in order to further test this hypothesis, we incorporated our data into a meta-analysis based on published literature on temporal responses in rodents, resulting in a combined dataset for 50 species from seven families worldwide; among these, 29 species showed no significant change, eight showed a significant increase in size, and 13 showed a decline in size. Using a binomial logistic regression model for these metadata, we found that none of our chosen life history or habitat predictors could significantly explain the probability of a temporal response to climate warming, reinforcing our conclusion based on the more detailed data from the six African species.

Mammalian body size is determined by interactions between climate, urbanization, and ecological traits

“…In another meta-analysis of 73 North American mammal species, McCain and King 30 found the largest mammals examined were 27 times more likely to respond to climate change compared to the smallest mammals. These previous studies are all limited in that they are meta-analyses (also see 71 ), vary in statistical approach, and do not leverage the dense intraspecific sampling we achieved here. Our work draws strength from the use of a single hierarchical modeling framework for separate measures of body mass and head-body length and reveals a robust signal of larger mammals being more sensitive to variation in temperature, and conforming to Bergmann’s Rule.…”

Fifty years of data show the effects of climate on overall skull size and the extent of seasonal reversible skull size changes in the common shrew

“…This outcome adds to the very mixed picture of the change in body size in mammals under global climate change. The analysis of 50 species of rodents from seven families revealed no significant temporal change in body size (represented mainly by skull dimensions) in 29 species, a significant decline in 13, and an increase in size in eight species (Nengovhela et al 2020). Of the three carnivore species in which skull size was measured in the second half of the 20th century and analysed in the context of climate change, skull size showed a significant increase in two species and a significant decline in the other (Yom-Tov et al 2008, 2010a, 2010b.…”

“…Although the majority of studies did not find significant temporal changes in the sizes of birds and mammals, there are many examples of long-term body size and body mass changes (recorded over one to several decades) correlated with global climate change. While a decrease in size is indeed the major response in birds, the situation is much less clear in mammals, where many species increase in size (Teplitsky and Millien 2014;Naya et al 2017;Nengovhela et al 2020). This increase in size is usually explained as a reaction to increased food availability as a result of increasing temperatures (Yom-Tov and Geffen 2011; Boutin and Lane 2014 and references cited therein).…”

Mammalian body size is determined by interactions between climate, urbanization and traits

“…In another metaanalysis of 73 North American mammal species, McCain & King (2014) found that the largest mammals examined were 27 times more likely to respond to climate change compared to the smallest mammals. These previous studies are all limited in that they are meta-analyses (also see Nengovhela et al 2020), vary in statistical approach, and do not leverage the dense intraspecific sampling we achieved here. Our work draws strength from the use of a single hierarchical modeling framework for separate measures of body mass and head-body length and reveals a robust signal of larger mammals being more sensitive to changes in temperature, and conforming to Bergmann's Rule.…”