Stoichiometric and stable isotope ratios of wild lizards in an urban landscape vary with reproduction, physiology, space and time.

Andrew M Durso,Geoffrey D Smith,Spencer B Hudson,Susannah S French,Steven Cooke

doi:10.1093/conphys/coaa001

Andrew M Durso, Geoffrey D Smith + Show 3 more

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https://doi.org/10.1093/conphys/coaa001

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Abstract

Spatial and temporal variation in stoichiometric and stable isotope ratios of animals contains ecological information that we are just beginning to understand. In both field and lab studies, stoichiometric or isotopic ratios are related to physiological mechanisms underlying nutrition or stress. Conservation and ecosystem ecology may be informed by isotopic data that can be rapidly and non-lethally collected from wild animals, especially where human activity leaves an isotopic signature (e.g. via introduction of chemical fertilizers, ornamental or other non-native plants or organic detritus). We examined spatial and temporal variation in stoichiometric and stable isotope ratios of the toes of Uta stansburiana (side-blotched lizards) living in urban and rural areas in and around St. George, Utah. We found substantial spatial and temporal variation as well as context-dependent co-variation with reproductive physiological parameters, although certain key predictions such as the relationship between δ15N and body condition were not supported. We suggest that landscape change through urbanization can have profound effects on wild animal physiology and that stoichiometric and stable isotope ratios can provide unique insights into the mechanisms underlying these processes.

Highlights

Landscape change through urbanization is a major factor influencing the distribution, conservation status, foraging behaviour and nutritional status of wildlife (Ditchkoff et al, 2006)
We examined a large data set on the stoichiometric (C:N) and stable isotope (δ13C and δ15N) ratios of wild lizards from populations that vary in their exposure to urbanization and anthropogenic stressors
We found that variation in δ13C at urban sites exceeded that at rural sites, which is consistent with the idea that resources at disturbed urban sites may be less optimal than those in relatively undisturbed rural areas

Summary

Introduction

Landscape change through urbanization is a major factor influencing the distribution, conservation status, foraging behaviour and nutritional status of wildlife (Ditchkoff et al, 2006). Nutritional stress due to habitat loss or alteration can contribute to wildlife declines (Suorsa et al, 2004, Amo et al, 2006, Naug, 2009, Vangestel et al, 2010). Nutritional stress can compromise individual health and thereby decrease survivorship, with potential conservation implications (McNamara and Houston, 1990, Wikelski and Romero, 2003, Romero and Wikelski, 2010). Warmer winters may increase energetic demand during hibernation, eating into energy budgets (Zani et al, 2012)

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