Torpor, arousal and activity of hibernating Greater Horseshoe Bats (Rhinolophus ferrumequinum)

Abstract

Summary1. Patterns of torpor, arousal and activity in free-living Greater Horseshoe Bats, Rhinolophus ferrumequinum (Schreber), were investigated during the hibernation period by using temperature-sensitive radio-transmitters. 2. Torpor bouts varied between 0·1 and 11·8 days, with individual means ranging from 1·3 to 7·4 days. Torpor bout duration decreased with increasing ambient temperature. 3. Activity duration varied from 37 min to 54 h 24 min, with individual means ranging from 2 : 29 to 8 : 58 h. Activity duration increased with ambient temperatures above approximately 10 ° C. 4. Ten of 11 bats synchronized their arousals with dusk. The circadian rhythm of one bat showed a free-running pattern over a period of about 5 weeks. Arousals were more highly synchronized, and closer to dusk, in individuals with lower body condition. 5. That bats forage in mild weather is supported by the strong synchronization of arousals with dusk, especially in bats with low body condition. 6. Patterns of torpor and subsequent activity are consistent with predictions that torpor lasts until a critical metabolic or water imbalance is achieved. Because metabolism and water loss are temperature-dependent, torpor bout duration decreases with increasing temperature. The imbalance is corrected during subsequent activity, which is relatively constant in duration until a temperature threshold of 10 ° C, above which increasing levels of foraging lead to longer activity bouts.

Sex and Age Related Habitat Selection and Mass Dynamics of Daubenton's BatsMyotis daubentonii(Kuhl, 1817) Hibernating in Natural Conditions

“…There could be, at least, two reasons for hibernating near the entrance to the gallery: (1) to minimise the metabolic rate by hibernating in low ambient temperature and higher relative humidity and (2) to synchronise the arousals frequency with the temperature outside hibernation site, to get information about possibility of foraging. It was shown that individuals of R. ferrumequinum over-wintering in natural conditions were able to detect temperature fluctuations outside the hibernation sites by choosing the roosting positions in parts of hibernation sites where temperature changes were correlated with changes of temperature outside hibernaculum (Ransome, 1971;Park et al, 1999;Park et al, 2000). Thus M. daubentonii in significantly lower body condition were probably hibernating closer to the mine entrance for both, basically energetic, reasons.…”

Ecological consequences of temperature regulation: Why might the mountain pygmy possumBurramys parvusneed to hibernate near underground streams?

“…There is growing evidence that unfavorable water balance during hibernation at least contributes to the necessity for periodic arousals to euthermia by hibernating mammals, and that factors affecting water balance during hibernation can impact on hibernation success. 15,[19][20][21][22] Here we determine for the endangered mountain pygmy possum the thermal, energetic and ecological consequences of ingesting water to overcome these hygric imbalances during hibernation. If hibernating mountain pygmy possums arouse to replenish their body water, then they must either drink liquid water or consume frozen water (snow or ice) while euthermic.…”

“…15 Indeed, a number of recent studies suggest that maintenance of water balance is a critical factor determining hibernation duration and success. [19][20][21][22] For torpid mammals, the only avenues of water gain and loss are metabolic water production and evaporative water loss. The ratio of these, relative water economy (relative water economy = metabolic water production/evaporative water loss), is therefore an index of the state of water balance for a torpid mammal.…”

Winter diet analysis in Rhinolophus euryale (Chiroptera)

“…The frequency of such breaks varies among species and individuals [1][2][3][4]. However, the causes of these arousals appear varied and uncertain, though temperature in the roost has been suggested to play an important role [5]. Breaks in hibernation can lead to changing the hibernation site, drinking or to foraging activity.…”