Profound reversible seasonal changes of individual skull size in a mammal

Lázaro, Javier; Dechmann, Dina K. N.; LaPoint, Scott D.; Wikelski, Martin; Hertel, Moritz

doi:10.1016/j.cub.2017.10.064

Cited by 9 publications

(7 citation statements)

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“…A recent study by Lazaro et al . () looked at the variation in terms of body and braincase sizes in relation to seasons in shrews ( Sorex araneus ). They found that there was a decrease in body mass just before the winter (17.6%) and then a dramatic increase of 83.4% in the spring.…”

Section: Discussionmentioning

confidence: 99%

Virtual endocasts of fossil Sciuroidea: brain size reduction in the evolution of fossoriality

et al. 2018

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Aplodontia rufa (mountain beaver) is the only extant member of the Aplodontidae. The fossil record indicates that this family displayed greater taxonomic and ecological diversity in the past, and that the burrowing adaptations of Aplodontia might be derived. We describe the first virtual endocasts of A. rufa and of three fossil aplodontids: Prosciurus relictus and Pros. aff. saskatchewaensis (early Oligocene), and Mesogaulus paniensis (early Miocene). Our results show that the endocasts of early aplodontid rodents are more similar to those of early arboreal squirrels than to those of the later occurring aplodontids in terms of both relative size and morphology. The endocranial features observed in sciurids and early aplodontids, missing in later aplodontids, have been associated with better vision and the development of arboreality in squirrels. Basal Aplodontidae known from postcrania have been described as generalists with some features for arboreality, which may provide a basis for these similarities. In contrast, the relatively small endocasts of the later occurring aplodontids, which lack traits related to visual specialization, may reflect their burrowing adaptations, as they would be less reliant on visual cues. When integrated with data from the most primitive fossil rodents, the Ischyromyidae, these new data suggest that early squirrels and aplodontids diverged from more terrestrial ischyromyids to become more arboreal, with relatively larger brains showing traits for improved vision. Recent Aplodontidae with fossorial adaptations returned to a more ischyromyid‐like condition in their endocranial features. These results are consistent with previous observations that changes in locomotion are reflected in the endocranial anatomy of rodents.

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Section: Discussionmentioning

confidence: 99%

Virtual endocasts of fossil Sciuroidea: brain size reduction in the evolution of fossoriality

et al. 2018

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“…First, they have basal metabolic rates of, on average, more than 300% of those predicted for non‐shrew mammals of their size, as well as greater average body temperatures than other shrews (Taylor, ). As a result of these high metabolic demands, Sorex shrews need to feed at least every few hours (Churchfield, ) and their body mass drops significantly in the winter (including reduction in brain size; Dehnel, ; Pucek, ; Lázaro, Dechmann, LaPoint, Wikelski, & Hertel, ). Second, unlike many other cold‐adapted mammals, Sorex shrews are not known to hibernate or use torpor in the winter (Taylor, ).…”

Section: Introductionmentioning

confidence: 99%

Do ecogeographical rules explain morphological variation in a diverse, Holarctic genus of small mammals?

Stanchak

Santana

2018

Journal of Biogeography

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Aim We use ecogeographical rules to understand the relationship between biogeography and morphological evolution in Sorex (Linnaeus, 1758) shrews. Specifically, we test for climatic correlations in body size (Bergmann's rule; larger species in colder habitats) and pelage brightness (Gloger's rule; darker species in more humid/warmer habitats). Location North America and Eurasia (Holarctic). Taxon Sorex spp. (Mammalia: Soricomorpha: Soricidae). Methods We compiled body size data for 51 species of Sorex and measured pelage brightness from museum specimens for 43 species. We sourced bioclimatic data across the geographical range of each species as well as specific to the museum specimen localities. For comparative purposes, we also estimated a Sorex phylogeny using existing sequence data. To test Bergmann's and Gloger's rules, we constructed phylogenetic least squares models considering latitude, altitude, and bioclimatic variables as predictors of interspecific variation in body size and pelage brightness across Sorex. We then performed these tests separately for the Palaearctic and Nearctic lineages. Results Sorex exhibits wide variation in both body size and pelage brightness. In models of the entire genus and of the Nearctic clade, neither trait is significantly predicted by the variables tested. A decrease in pelage brightness in the Palaearctic clade is significantly predicted by increasing mean annual temperature and annual precipitation, but only when considering climatic data specific to the measured specimen localities. Main conclusions Sorex does not conform to Bergmann's rule. This result aligns with intraspecific studies suggesting Bergmann's rule is less evident in smaller taxa, but it counters others that found support for the rule in North American and European assemblages. Different patterns in pelage evolution across the Nearctic and Palaearctic clades may result from different historical climatic pressures; however, the significance of the relationship between climate and pelage evolution is dependent on the specificity of the climatic data. Sorex may be a useful focal taxon for exploring the relationship between intra‐ and interspecific ecogeographical patterns as well as the relative roles of morphological, behavioural, physiological, and life history characteristics in explaining the ability to persist in climatically challenging environments.

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“…Over the course of a full annual cycle, animals may change their foraging behavior (Dearing ), diet (Nadjafzadeh et al ), movement strategies (Newton ), space use (Sumasgunter et al ), energy budget (Czenze et al ), gonad size and sexual behavior (Gill ), and brain size, cranial morphology, and metabolic rate (Lázaro et al ). This variation is often driven by seasonal fluctuations in either resource availability or reproductive physiology.…”

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confidence: 99%

Spatial and temporal patterns in age structure of Golden Eagles wintering in eastern North America

et al. 2020

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The behavior of wildlife varies seasonally, and that variation can have substantial demographic consequences. This is especially true for long‐distance migrants where the use of landscapes varies by season and, sometimes, age cohort. We tested the hypothesis that distributional patterns of Golden Eagles (Aquila chrysaetos) wintering in eastern North America are age‐structured (i.e., birds of similar ages winter together) through the analysis of 370,307 images collected by motion‐sensitive trail cameras set over bait during the winters of 2012–2013 and 2013–2014. At nine sites with sufficient data for analysis, we documented 145 eagle visits in 2012–2013 and 146 in 2013–2014. We found significant between‐year variation in age structure of wintering eastern Golden Eagles, driven largely by annual differences in the proportion of first‐winter birds. However, although many other species show spatial structure in wintering behavior, our analysis revealed no latitudinal organization among age cohorts of wintering eastern Golden Eagles. The lack of age‐related latitudinal segregation in wintering behavior does not exclude the possibility that these eagles have sex‐based or other types of dominance hierarchies that could result in spatial or temporal segregation. Alternatively, other mechanisms such as food availability or habitat structure may determine the distribution and abundance of Golden Eagles in winter.

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Profound reversible seasonal changes of individual skull size in a mammal

Cited by 9 publications

References 0 publications

Virtual endocasts of fossil Sciuroidea: brain size reduction in the evolution of fossoriality

Virtual endocasts of fossil Sciuroidea: brain size reduction in the evolution of fossoriality

Do ecogeographical rules explain morphological variation in a diverse, Holarctic genus of small mammals?

Spatial and temporal patterns in age structure of Golden Eagles wintering in eastern North America

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