Climatic correlates of migrant Natal long-fingered bat (Miniopterus natalensis) phenology in north-eastern South Africa

Abstract

ContextFor migratory animals, particularly those with long generation times, changing weather patterns may cause a mismatch between periods of expected and actual resource availability, termed phenological mismatch. The cave-dwelling Natal long-fingered bat (Miniopterus natalensis) is a regional migrant within South Africa for which the (hitherto unknown) phenology of migration may be affected by climate. AimsTo investigate the migration phenology of the Natal long-fingered bat in relation to climate at a maternity cave in South Africa. MethodsFive years (2014–18) of echolocation data from a maternity cave site in Limpopo, South Africa, were studied. Separate stepwise General Linear Models (GLMs) were constructed for each season using photoperiod, minimum temperature, dew point, rainfall, barometric pressure, humidity and maximum wind speed. Arrival and departure dates among years were also compared. Key resultsPhotoperiod had the greatest effect on the magnitude of Natal long-fingered bat phenological patterns in activity across all seasons. Although spring (September - November) arrival at the maternity site was variable across years, summer departure dates did not differ, resulting in a shorter breeding period in the 2017–18 sample year. During the 2016–17 sample year, the magnitude of Natal long-fingered bat activity was significantly lower than in other years, which coincided with El Niño-induced drought conditions and likely impacted resources and led to a reduction in activity and population size. ConclusionsPhotoperiod is a strong predictive cue of the phenology of migration of the Natal long-fingered bat and likely cues migration for this species. The narrow departure dates of these bats from the maternity site supports these results. ImplicationsThe present study indicates that Natal long-fingered bats use photoperiod as a migration cue and do not appear to shift their spring–summer breeding season, likely making them vulnerable to phenological mismatch and population decline. The research highlights the need for systematic population monitoring for the Natal long-fingered bat.

No Evidence of Pre-Hibernation or Pre-Migratory Body Mass Gain in Miniopterus natalensis in North-Eastern South Africa

“…It is possible that nonscrotal male M. natalensis do not show the expected autumnal increase in body mass because they do not migrate and remain at the maternity cave, as suggested by the male-only sex ratio observed during winter. These males also may not fatten for hibernation because the population remaining at the Madimatle maternity cave continue to forage throughout winter (Pretorius et al 2020). Male M. natalensis do, however, increase body mass during summer in preparation for mating, with scrotal males increasing their body mass by approximately 8%.…”

“…Subsequently, the duration of the gestation period is eight months (van der Merwe 1980(van der Merwe , 1987. Females then consistently depart the maternity site en masse during early February (Pretorius et al 2020). In males, spermatogenesis occurs in summer and sperm may then be stored in the testes for up to five months (van der Merwe 1987).…”