Interspecific cohabitation of maternity colonies of Nyctalus noctula and Myotis daubentonii (Chiroptera: Vespertilionidae) in a single roost feature in the West Midlands, UK

Morgan Hughes, Colin Cross, Scott Brown

Abstract: Woodland bat species may ‘time share’ tree roost features and occasionally have been recorded cohabiting in low numbers. However, few observations exist of substantial maternity roosts of sympatric species cohabiting in a single roost feature. Following an emergence survey in June of 2021 of a known maternity roost of 28 Nyctalus noctula individuals (pre-parturition), a further emergence from the same feature of 59 Myotis daubentonii was recorded and filmed using infra-red and thermal cameras. Cohabitation records of maternity colonies of this size have not been previously submitted to the UK Bat Tree Habitat Key database, nor do similar observations appear in the literature. Following the 2021 destruction of the roost feature during a storm, we were able to describe the entire feature in detail, including transverse section analysis and photography. Subsequent surveys have now shown that these two bat species have cohabited in features in at least three separate trees within the study site (a small, suburban, broad-leaved woodland), over at least two seasons. This novel record of interspecific cohabitation not only adds to the body of knowledge regarding roost cohabitation of Vespertilionidae in temperate woodlands, but also highlights the value of infra-red and thermal optics for improving the efficacy of bat emergence surveys, particularly in forest habitats.

Primer registro de asimetría morfológica en extremidades posteriores en Lasiurus cinereus (Chiroptera: Vespertilionidae) en México

Sergio Albino-Miranda, E. Vanessa Díaz-Ortiz, Karla P. Borges-Jesús, José D. Cú-Vizcarra

Resumen: Los reportes sobre las anomalías morfológicas en vertebrados son escasos y apuntan a una mayor frecuencia en zonas anatómicas que no afectan la supervivencia del organismo. En este trabajo reportamos el hallazgo de una hembra adulta del murciélago canoso (Lasiurus cinereus), con extremidades posteriores asimétricas debido a una anomalía morfológica en una de sus patas. Las medidas morfológicas del espécimen fueron comparadas con individuos de colección y se analizó si la diferencia entre las medidas de sus extremidades izquierdas y derechas era la esperada bajo un modelo aleatorio. Los datos aquí presentados muestran una menor longitud en la pata izquierda en comparación con su población en Norteamérica. No se observó una variación significativa diferente al azar entre los lados de las extremidades posteriores ni anteriores. Debido a que las anomalías fenotípicas pueden ser evidencia de situaciones de estrés en las poblaciones silvestres, el reporte de estas variaciones es importante dada la escasez de información sobre este tópico.

Abstract: The records of morphological abnormalities in vertebrates are scarce and most of them have been recorded on anatomic zones that do not affect individual survivorship. In this work, we report the finding of an adult female hoary bat (Lasiurus cinereus), with an asymmetric hind limb due to a morphological abnormality. We compared the morphological measurements of the specimen with individuals from the collection and we tested if the difference between forelimbs and hind limbs was the expected under a random model. The data presented here show a lower length in the left foot of the specimen compared to the North American hoary bat populations. No significant variation other than chance was observed between the hindlimb and forelimb sides. Since phenotypic abnormalities can be evidence of stress situations in wildlife populations, reporting these variations is important given the scarcity of information on this topic.

Long-term monitoring of temperature effect on the population dynamics of the only overwintering colony of Myotis blythii in the Iberian Peninsula

Juan Ramón Boyero, Olvido Tejedor

Abstract: Hibernation is a critical period for the survival of bats in temperate regions. In Southern Europe in particular, the hibernation of some species is hampered by the scarcity of winter roosts with temperatures low enough to reach a deep hibernation state, which involves physiological processes other than daily torpor. In this paper we present the results of the study on various aspects of the only known wintering colony of the lesser mouse-eared bat (Myotis blythii) in Spain. Located in a cave in the Sierra de las Nieves National Park (Málaga), the colony has been monitored for ten years by means of photographic censuses and climatic data recording. As a result, it has been determined that at least 93.75% of the colony belongs to Myotis blythii. The characteristic whitish tuft between the ears, present in a variable proportion in European M. blythii, was in at least 85% of the individuals. The population fluctuates during the period of roost occupation, from September to May, reaching a maximum in March 2010 when up to 1517 bats were counted. In this month the temperature of the roost reached its minimum: 4.02 °C ± 1.18 (mean ± SD). The population was distributed in groups of different sizes with a mean of 35.50 individuals ± 76.54 (mean ± SD), ranging from solitary individuals (1.0% of the total observed) to clusters of more than 600 bats. Overall, we found that temperature had an inverse relationship on the cluster size, while water vapor pressure deficit had a direct relationship. Specifically, the best fit was for the mean temperature and mean water vapor pressure deficit for the previous 15 days. Climate change, to which the Mediterranean region is especially vulnerable, may alter the conditions of this refuge, posing a threat to this unique colony.

Impact of reproduction on roost selection of the Indian flying fox, Pteropus medius (Temminck, 1825)

Vadamalai Elangovan

Abstract: A thorough knowledge of ecology and behaviour is a probable requirement for proper conservation and management of a species. The Indian flying fox, Pteropus medius (formerly P. giganteus Brünnich, 1782), lives gregariously in large trees and spends a considerable time at day roosts and the roost sites of tree-dwelling bats play vital roles in survival, reproduction and population persistence. This study describes changes in roost selection, colony size and behaviours of P. medius during reproductive and non-reproductive seasons. The colony size of P. medius was significantly low during the summer non-reproductive season (486.5 ± 121.1 SD) than the spring (1942 ± 488.8 SD) and monsoon (2367.7 ± 277 SD) reproductive seasons. The number of roost trees utilized and roost site selection differed across the reproductive and non-reproductive seasons. The bats occupied the southern periphery of the garden during the non-reproductive period (summer), whereas they shifted to the central and northern parts of the garden during the reproductive seasons and winter periods. The reproductively active individuals secluded themselves from the reproductively inactive colony members. The selection of secluded roost sites during the reproductive period demonstrates the need for social exclusion, less disturbance, and reduced mate competition during the reproductive phase. The higher population size during the reproductive period might be due to the immigration of bats, most probably male individuals. This could facilitate gene flow from nearby populations and thus increase genetic diversity and better adaptations, increasing species sustainability.