A review of the physiology of a survival expert of big freeze, deep snow, and an empty stomach: the boreal raccoon dog (Nyctereutes procyonoides)

Review
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Abstract

The raccoon dog (Nyctereutes procyonoides) is an invasive canid originating from eastern Asia. Here, we review its physiological adaptations to wintering, with an emphasis on northern Europe, where the raccoon dog spends the coldest part of the year in winter sleep. The timing of physiological changes related to wintering is connected to photoperiod by melatonin. In preparation to winter, raccoon dogs display autumnal hyperphagia and fattening probably regulated by the interaction of several peptide hormones. Sufficient fat deposition is essential for survival through the cold season and for reproduction in spring. The wintering strategy includes alternating periods of physical activity and passivity. Effective arousal and foraging during warmer bouts are enabled by normoglycaemia. During active periods, raccoon dogs are opportunistic participants in the food web, and they mainly utilize ungulate carcasses, plant material, and small mammals. Preferred wintertime habitats include watersides, forests, wetlands, and gardens. However, many food items become limited in mid-winter and snow restricts foraging leading to a negative energy balance. During passivity, energy is preserved by denning and by modest metabolic suppression, probably enabled by decreased thyroid hormone levels. Sleepiness and satiety could be maintained by high growth hormone and leptin concentrations. Several hormones participate in the extension of phase II of fasting with selective fatty acid mobilization and efficient protein conservation. The blood count, organ function tests, bone mass, and bone biomechanical properties exhibit high resistance against catabolism, and breeding can be successful after significant weight loss. The flexible physiological response to wintering is probably one reason enabling the successful colonization of this species into new areas.

Keywords

Fasting Fatty acid mobilization Passive wintering Seasonal endocrinology Winter sleep 

Abbreviations

AA

Amino acid

BM

Body mass

FA

Fatty acid

GH

Growth hormone

MR

Metabolic rate

MUFA

Monounsaturated fatty acid

PUFA

Polyunsaturated fatty acid

PYY

Peptide YY

SC

Subcutaneous

SFA

Saturated fatty acid

T3

Triiodothyronine

T4

Thyroxine

Ta

Ambient temperature

TAG

Triacylglycerols

Tb

Body temperature

UFA

Unsaturated fatty acid

Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Faculty of Health Sciences, School of Medicine, Institute of Biomedicine/AnatomyUniversity of Eastern FinlandKuopioFinland
  2. 2.Faculty of Science and Forestry, Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland

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