Effect of age and ration on diet-tissue isotopic (Δ¹³C, Δ¹⁵N ) discrimination in striped skunks (Mephitis mephitis)

† Contribution to Special Section ‘Stable Isotopes in Mammals’.

Abstract

An important prerequisite for the effective use of stable isotopes in animal ecology is the accurate assessment of isotopic discrimination factors linking animals to their diets for a multitude of tissue types. Surprisingly, these values are poorly known in general and especially for mammalian carnivores and omnivores in particular. Also largely unknown are the factors that influence diet-tissue isotopic discrimination such as nutritional quality and age. We raised adult and juvenile striped skunks (Mephitis mephitis) in captivity on a constant omnivore diet (Mazuri Omnivore A 5635). Adults (n=6) and juveniles (n=3) were kept for 7 months and young (n=7) to the age of 50 days. We then examined individuals for stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values of hair, nails, lipid, liver, muscle, bone collagen and the plasma, and cellular fractions of blood. Discrimination values differed among age groups and were significantly higher for young compared with their mothers, likely due to the effects of weaning. Δ¹⁵N isotopic discrimination factors ranged from 3.14 (nails) to 5.6‰ (plasma) in adults and 4.3 (nails) to 5.8‰ (liver) for young. For Δ¹³C, values ranged from−3.3 (fat) to 3.0‰ (collagen) in adults and from−3.3 (fat) to 2.0‰ (collagen) in young. Our data provide an important tool for predicting diets and source of feeding for medium-sized mammalian omnivorous adults integrated over short (e.g. liver, plasma) through long (e.g. collagen) periods and underline the potential effects of age on isotopic values in omnivore diets.

Keywords:

• age
• carbon-13
• isotope ecology
• isotopic discrimination
• nitrogen-15
• nutrition
• striped skunk

Acknowledgements

We thank Seth Cherry and Jason Pitt for assistance with animal care and tissue sampling. This study was conducted in accordance with the guidelines of the CCAC under permit (20100084) issued by the University of Saskatchewan.We thank G. Strauch and two anonymous reviewers for critical comments on an earlier draft of the manuscript.

Funding

This work was supported by the Environment Canada, University of Saskatchewan and the Delta Waterfowl and Wetlands Association.

Notes

† Contribution to Special Section ‘Stable Isotopes in Mammals’.