In February 2008, three white-nosed coatis (Nasua narica) were found dead in a recreational park in Cancun, Mexico. The diagnosis of rabies virus (RABV) infection was confirmed by direct immunofluorescence test. The phylogenetic analysis performed with the complete RABV nucleoprotein gene positioned this isolate close to a sequence of a human rabies case reported during 2008 from Oaxaca, Mexico, sharing 93% similarity. In turn, these two variants are related to another variant found in rabid Tadarida brasiliensis mexicana bats across North America. Anti-RABV neutralizing activity (1·3 IU/ml) was found in the serum of one white-nosed coati captured with another five that cohabited with the dead animals. Enhanced rabies surveillance and pathogenesis studies should be conducted in coatis and insectivorous bats of the region to clarify the role of these species as potential emergent or long-term unidentified RABV reservoirs.

During late autumn insectivorous bats must deposit a fat store to cover their energy demands throughout the period of hibernation, yet the density of aerial insects by this time has already declined from its peak in midsummer. Krzanowski (1961) suggested that bats are able to deposit a fat store by manipulating their energy expenditure; specifically by selecting cold roosting locations rather than warm roosts, and depressing their body temperatures during the day roosting period. It was hypothesized that these behavioural changes result in very low daily energy demands, and despite reduced food intake the animals are still able to gain body fat. We made several tests of this hypodiesis. First, we explored the thermo-selection behaviour of long-eared bats (Plecotus auritus) in the summer and in the pre-hibernal period. We found that in summer bats preferred temperatures of about 32–35° (about thermoneutral), but in the pre-hibernal period they preferred much colder temperatures of about 10°. Second, using open-flow respirometry we found that in the cold pre-hibernal bats entered torpor for an average of 14 h each day. Compared with bats held at 30° (that did not go torpid), the bats at 7° expended less energy. The extent of saving was sufficient to positively affect their mass balance, despite the fact that bats at lower temperature also had reduced digestive efficiencies. Our findings support the hypothesis that during the pre-hibernal period insectivorous bats manipulate their mass balance primarily by alterations in their energy expenditure, specifically utilizing energy-sparing mechanisms such as torpor.

Factors influencing prey selection by insectivorous bats are poorly understood but may be related to interspecific differences in echolocation call structure. The diet of Eptesicus fuscus was compared with prey abundance across a foraging season to examine prey selection by a bat species which has an echolocation call dominated by a frequency-modulated (FM) component. Guano samples were collected on 18 occasions from a single colony between May and September 2000. Abundance of aerial insects was measured using a black-light trap on nights when guano was collected. Regression analysis was used to test the hypotheses that E. fuscus: (1) does not take prey in proportion to their relative abundance; (2) forages preferentially for beetles in a manner predicted by foraging theory. Relative abundance (= proportion in relation to other prey types) of prey in trap samples was not a good predictor of prey in the diet across periods or within periods, which suggests selective foraging. Beetles (42–96% of the diet by per cent volume) were consistently eaten in higher proportions than their relative abundance. The absolute abundance of beetles (= abundance irrespective of the abundance of other prey types) explained 60% of the variation in beetle use with more beetles eaten when they were abundant. Absolute beetle abundance explained 66%, 53% and 47% of the variation in the use of three other prey types, with more of these prey eaten when beetle abundance was low. Finally, absolute beetle abundance explained 60% of the variation in diet breadth, which increased when beetle abundance was low. Our results agree with predictions derived from foraging theory and support the hypothesis that E. fuscus forages selectively for beetles, consuming a wider variety of prey when beetle abundance is low. These results are similar to those found for the greater horseshoe bat Rhinolophus ferrumequinum which has an echolocation call dominated by a constant-frequency (CF) component, and suggest that some FM bats may discriminate among prey taxa, at least at the ordinal level.

The echolocation calls of insectivorous bats of the northern Yucatan Peninsula, Mexico, with the exception of the phyllostomids and molossids, are presented. The aim is to provide a catalogue of bat sounds that can be used for acoustic inventories of insectivorous bats using the Pettersson heterodyne and time-expansion bat detectors. The acoustic method can be used alone or in combination with inventories based on mist-netting, a method more suitable for the low-intensity echolocators (mainly the phyllostomids), which are difficult to monitor acoustically. The insectivorous species of the Yucatan are generally easy to identify by their echolocation calls, particularly when combined with visual observations of foraging bats at dusk.

The purpose of this study was to evaluate the impact of moonlight on the swarming activity of bats at an abandoned mine in southern Sweden. The mine serves as a hibernaculum for six species of insectivorous bats. Swarming activity at one of the mine entrances was measured on 12 nights between 1 August and 8 September 2000, by electronically counting the number of bats passing through an opening (about 30×40 cm) leading to a mine tunnel. The number of bat passes outside the mine was also counted, using a bat detector. Most bats were males, as confirmed by mist-netting outside the mine. Low frequency vocalizations, indicating territorial interactions, were heard frequently. The number of bats entering the mine was closely correlated with the number of bats flying outside, and neither was affected by moonlight. We conclude that the insectivorous bats at high latitudes may not have been exposed to significant nocturnal predator pressure, leading to the evolution of lunar phobia, as have many tropical bats.