How to spend the summer? Free-living dormice (Glis glis) can hibernate for 11 months in non-reproductive years.

Journal of Comparative Physiology B 185(8):931–939.

Abstract:

Edible dormice are arboreal rodents adapted to yearly fluctuations in seed production of European beech, a major food source for this species. In years of low beech seed abundance, dormice skip reproduction and non-reproductive dormice fed ad libitum in captivity can display summer dormancy in addition to winter hibernation. To test whether summer dormancy, that is, a very early onset of hibernation, actually occurs in free-living dormice, we monitored core body temperature (Tb) over ~12 months in 17 animals during a year of beech seeding failure in the Vienna Woods. We found that 8 out of 17 dormice indeed re-entered hibernation as early as in June/July, with five of them having extreme hibernation durations of 11 months or more (total range: 7.8–11.4 months). Thus, we show for the first time that a free-living mammal relying on natural food resources can continuously hibernate for >11 months. Early onset of hibernation was associated with high body mass in the spring, but the distribution of hibernation onset was bimodal with prolonged hibernation starting either early (prior to July 28) or late (after August 30). This could not be explained by differences in body mass alone. Animals with a late hibernation onset continued to maintain high nocturnal Tb’s throughout summer but used short, shallow torpor bouts (mean duration 7.44 ± 0.9 h), as well as occasional multiday torpor for up to 161 h.

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[hölzl]

Seasonal Body Weight Changes in Pygmy Lorises (Nycticebus pygmaeus).

Verh.ber. Erkrg. Zootiere 42: 292-298

Summary:

Obesity has often been considered a main health problem of captive pygmy lorises. In fact changes in bodyweight might not always be pathological but an important aspect of the animals’ physiology. Kept under natural light ing and climatic conditions, pygmy lorises show distinct weight changes independent from the food supply. These changes are correlated to the season and pygmy lorises have significantly higher bodyweights in the winter than in the summer months.

Peak bodyweight values in winter are more than 50 % higher than the lowest values in summer.

The variation in bodyweight occurs in both sexes and equally in pregnant and non-pregnant females. Food sources are scarce during the winter season and pygmy lorises seemingly increase their daily food intake in order to accumulate fat reserves prior to the time of food shortage. For pygmy lorises, energy storage appear s to be an important means to allow survival during the winter months.

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