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

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.

Role of Brown and Beige Adipose Tissues in Seasonal Adaptation in the Raccoon Dog (Nyctereutes procyonoides)

“…Animals that are subjected to non-pathological body weight cycles according to seasonal phases and the environmental temperature changes offer an interesting model to study the signals triggering WAT browning and the physiological relevance of beige adipose tissue. Our model species, the raccoon dog, is a middle-sized omnivorous canid species that undergoes repeated and drastic seasonal body weight and adiposity fluctuations [15]. Raccoon dogs can almost double their weight with the accumulated body fat storages after summer as they prepare for the winter food scarcity.…”

“…The raccoon dog can also enter a light hypometabolic state to preserve energy. During the winter sleep, the raccoon dog undergoes a relatively shallow hypothermia (body temperature (T B ) reduction only 0.5-1.5 • C) as compared to other winter sleeping species, e.g., the brown bear (Ursus arctos arctos), which reduces its' T B by 4-5 • C [15,19]. Hibernating animals undergo a more complete metabolic depression and T B reduction [20], and BAT activity decreases as the body temperature is reduced in order to change to the energy-saving hibernation T B in the colder climate.…”

Nature of Evidence in Religion and Natural Science

“…81 However, as long as narratives or anecdotes can provide research ideas and testable hypotheses to be studied further, they can be useful as inspiration for systematic research. 82 The demarcation between science and belief-based systems that sometimes take the appearance of science can be exemplified by examining some pseudoscientific theories. Complementary and alternative medicine (CAM) justifies itself based on personal experiences rather than objective evidence.…”

Effect of Feeding Intensity on Metabolic Maintenance, Reproduction and Welfare in Blue Fox (Vulpes lagopus)

“…It seems that the reason for declined whelping result recently observed in blue foxes is the same as in the mink: disturbed energy balance due to excessive autumn fattening followed by a heavy slimming before breeding season. Typically energy intake, body condition and reproductive function are highly related to each other (Blance et al 2003;Nieminen et al 2004;Asikainen 2013;Mustonen and Nieminen 2017;Kempe 2018). Sufficient balance between energy intake and energy consumption is a prerequisite for a good reproduction capacity.…”