Pregnancy during hibernation in Japanese black bears: effects on body temperature and blood biochemical profiles

Shimozuru, Michito; Iibuchi, Ruriko; Yoshimoto, Taichiro; Nagashima, Akiko; Tanaka, Jun; Tsubota, Toshio

doi:10.1644/12-mamm-a-246.1

Cited by 49 publications

(16 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As hypothesized, pregnant females that carried their foetus to term exhibited a high degree of homeothermy during the gestation period. This pattern resembles that observed in other mammals, such as bears 13 . However, while Thiel et al 11 also reported more stable T b in pregnant wolverines as compared to non-pregnant ones, they found that wolverines lowered their T b during gestation.…”

Section: Discussionsupporting

confidence: 87%

“…Few studies have examined the interplay between reproduction and body temperature variability in large, wild mammals. For example, pregnant African lions (Panthera leo) lower and stabilize their body temperature (hereafter T b ) to avoid episodes of hyperthermy 10 , and wolverines (Gulo gulo) 11 also lower their T b during pregnancy despite living in cold environments, whereas hibernating bears exhibit a high degree of homeothermy during pregnancy 12,13 . Also Svalbard reindeer (Rangifer tarandus platyrhynchus) lower their T b in winter, and some differences in T b patterns between reproductive and non-reproductive reindeer has been reported 5 , but the linkage between T b and reproductive status remains unclear.…”

mentioning

confidence: 99%

See 1 more Smart Citation

On the interplay between hypothermia and reproduction in a high arctic ungulate

Schmidt

Grøndahl

Evans

et al. 2020

Sci Rep

View full text Add to dashboard Cite

For free-ranging animals living in seasonal environments, hypometabolism (lowered metabolic rate) and hypothermia (lowered body temperature) can be effective physiological strategies to conserve energy when forage resources are low. to what extent such strategies are adopted by large mammals living under extreme conditions, as those encountered in the high Arctic, is largely unknown, especially for species where the gestation period overlaps with the period of lowest resource availability (i.e. winter). Here we investigated for the first time the level to which high arctic muskoxen (Ovibos moschatus) adopt hypothermia and tested the hypothesis that individual plasticity in the use of hypothermia depends on reproductive status. We measured core body temperature over most of the gestation period in both free-ranging muskox females in Greenland and captive female muskoxen in Alaska. We found divergent overwintering strategies according to reproductive status, where pregnant females maintained stable body temperatures during winter, while non-pregnant females exhibited a temporary decrease in their winter body temperature. these results show that muskox females use hypothermia during periods of resource scarcity, but also that the use of this strategy may be limited to non-reproducing females. Our findings suggest a trade-off between metabolically-driven energy conservation during winter and sustaining foetal growth, which may also apply to other large herbivores living in highly seasonal environments elsewhere.

show abstract

Section: Discussionsupporting

confidence: 87%

mentioning

confidence: 99%

On the interplay between hypothermia and reproduction in a high arctic ungulate

Schmidt

Grøndahl

Evans

et al. 2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…A drop in body temperature at parturition has been reported previously for American and Asiatic black bears and brown bears; in both species of black bears, the body temperature decreased to the level of nonpregnant bears after parturition [41], [42]. However, our results for brown bears showed that the body temperature during lactation did not fall as low as that of nonlactating bears, as also reported by Hissa [40] for brown bears.…”

Section: Discussionsupporting

confidence: 83%

“…The body temperature T(b) of pregnant females bears is on average higher and more stable during the period of gestation than that of nonpregnant females [40] , [41] . After parturition, T(b) drops to the level of nonpregnant bears [41] , [42] . We defined the hibernation period as 1 November until 31 March [48] , [49] and calculated the mean body temperature during hibernation for each individual.…”

Section: Methodsmentioning

confidence: 97%

See 1 more Smart Citation

Factors Affecting Date of Implantation, Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

Friebe

Evans²,

Arnemo

et al. 2014

PLoS ONE

View full text Add to dashboard Cite

Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

show abstract

Thermoregulation and energetics in hibernating black bears: metabolic rate and the mystery of multi-day body temperature cycles

2015

View full text Add to dashboard Cite

Black bears overwintering in outdoor hibernacula in Alaska decrease metabolism to as low as 25 % basal rates, while core body temperature (T(b)) decreases from 37 to 38 °C to a mid-hibernation average of 33 °C. T b develops cycles of 1.6-7.3 days length within a 30-36 °C range, with no circadian component. We do not know the mechanism or function underlying behind the T(b) cycles, although bears avoid T(b) of <30 °C and shorter cycles are predicted from higher rates of heat loss in colder conditions. To test this we manipulated den temperatures (T(den)) of 12 hibernating bears with body mass (BM) from 35.5 to 116.5 kg while recording T(b), metabolic rate (M), and shivering. T b cycle length (0.8-11.2 days) shortened as T den decreased (partial R(2) = 0.490, p < 0.001). Large bears with low thermal conductance (TC) showed more variation in T b cycle length with changes in T(den) than did smaller bears with high TC. Minimum T b across cycles was not consistent. At low T(den) bears shivered both during rising and decreasing phases of T(b) cycles, with minimum shivering during the fastest drop in T(b). At higher T den the T b pattern was more irregular. Mean M through T(b) cycles was negatively correlated to T den below lower critical temperatures (1.4-10.4 °C). Minimum M (0.3509 W/kg ± 0.0121 SE) during mid-hibernation scaled to BM [M (W) = 1.217 × BM (kg)(0.6979), R(2) = 0.855, p < 0.001]. Hibernating thermal conductance (TC) was negatively correlated to BM (R(2) = 0.721, p < 0.001); bears with high TC had the same T(b) cycle length as bears with low TC except at high T(den), thus not supporting the hypothesis that cooling rate alone determines T(b) cycle length. We conclude that T(b) cycling is effected by control of thermoregulatory heat production, and T(b) cycling may not be present when hibernating bears use passive thermoregulation. More intense shivering in the rising phase of cycles may contribute to the prevention of muscle disuse atrophy. Bears hibernating in cold conditions use more energy during hibernation than in warmer conditions. At T den below lower critical temperature, no extra energy expenditure results from T b cycling compared to keeping a stable T(b.)

show abstract

Pregnancy during hibernation in Japanese black bears: effects on body temperature and blood biochemical profiles

Cited by 49 publications

References 43 publications

On the interplay between hypothermia and reproduction in a high arctic ungulate

On the interplay between hypothermia and reproduction in a high arctic ungulate

Factors Affecting Date of Implantation, Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

Thermoregulation and energetics in hibernating black bears: metabolic rate and the mystery of multi-day body temperature cycles

Contact Info

Product

Resources

About