title: Growth overshoot and seasonal size changes in the skulls of two weasel species.
abstract: Ontogenetic changes in mammalian skulls are complex. For a very few species (i.e. someSorexshrews), these also include seasonally driven, bidirectional size changes within individuals, presumably to reduce energy requirements during low resource availabilities. These patterns are poorly understood, but are likely most pronounced in high-metabolic species with limited means for energy conservation. We used generalized additive models to quantify the effect of location, Julian day, age and sex on the length and depth of 512 and 847 skulls of stoat (Mustela erminea) and weasel (M. nivalis) specimens collected throughout the northern hemisphere. Skull length of both species varies between sexes and geographically, with stoat skull length positively correlated with latitude. Both species demonstrate seasonal and ontogenetic patterns, including a rare, absolute growth overshoot in juvenile braincase depth. Standardized braincase depths of both species peak in their first summer, then decrease in their first winter, followed by a remarkable regrowth that peaks again during their second summer. This seasonal pattern varies in magnitude and timing between geographical regions and the sexes, matching predictions of Dehnel's phenomenon. This suggests implications for the evolution of over-wintering strategies in mammals, justifying further research on their mechanisms and value, with implications for applied osteology research.
authors.affiliation: Department of Migration and Immuno-Ecology , Max Planck Institute for Ornithology , Am Obstberg 1, Radolfzell 78315 , Germany.
authors.forename: Scott
authors.identifier: 0000-0002-5499-6777
authors.initials: S
authors.lastname: LaPoint
authors.affiliation: Department of Biology , University of Konstanz , Universitätsstrasse 10, Konstanz 78457 , Germany.
authors.forename: Lara
authors.initials: L
authors.lastname: Keicher
authors.affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, Am Obstberg 1, Radolfzell 78315, Germany; Department of Biology, University of Konstanz, Universitätsstrasse 10, Konstanz 78457, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wikelski
authors.affiliation: Mammal Research Institute , Waszkiewicza 1, Białowieża 17-230 , Poland.
authors.forename: Karol
authors.initials: K
authors.lastname: Zub
authors.affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, Am Obstberg 1, Radolfzell 78315, Germany; Department of Biology, University of Konstanz, Universitätsstrasse 10, Konstanz 78457, Germany.
authors.forename: Dina K N
authors.initials: DK
authors.lastname: Dechmann
keywords: Dehnel's phenomenon; Mustela; body size; morphology; ontogeny; sexual dimorphism