Structural, temporal and genetic properties of social groups in the short-lived migratory bat Nyctalus leisleri

Abstract

Social groups of bats that operate under fission–fusion dynamics tend to establish and maintain non-random associations. We examined the social and genetic structure of the Leisler’s bat (Nyctalus leisleri), a species that is typical of tree-dwelling and long-distance migratory species in Europe. We used long-term co-occurrence data (capture-recapture sampling of roosting individuals) in combination with individual genetic relatedness (inferred from a set of microsatellite markers) to assess relationships between structural, temporal and genetic properties of roosting groups. Our results showed that social structure in groups of roosting Leisler’s bat was not random. Social clusters revealed by network analysis were almost identical to demographic cohorts, which indicates that Leisler’s bats are able to maintain social bonds only over a single season. After the period of active maternal care, roosting groups became smaller with a significantly higher level of genetic relatedness among adult females in contrast to the pregnancy and lactation stages. This provides some evidence that temporal social associations may be positively correlated with genetic relatedness. Low recapture rates of bats across seasons in light of natal philopatry indicates a shorter life span of individuals likely due to high mortality during long distance migratory movements. This probably has the most significant effect on the social system of this species.

Kin structure and roost fidelity in greater noctule bats

“…It is important to add that occasions of social grooming occurred strictly among members of the same social groups (Kozhurina, 1993). A more recent study of the temporal and genetic components of associative dynamics in Nyctalus leisleri also found a stronger impact of cohort year on the composition of social groups inferred through network analysis (Naďo et al, 2017). As pointed out by the authors, although genetic relatedness was also observed to significantly impact association between dyads, this could be the result of different genetic profiles between cohorts due to male-biased gene flow.…”

“…Studies monitoring roost associations have shown females will roost preferentially with some females rather than others, resulting in a non-random association pattern within the colony (e.g. Willis & Brigham, 2004;Metheny et al, 2008;Patriquin et al, 2013;Naďo et al, 2017).…”

An agent-based algorithm resembles behaviour of tree-dwelling bats under fission–fusion dynamics

“…For roost switching simulations, we designed an area of 128.2 ha (~ 900 × 1800 m) with a 3-dimensional configuration identical to habitat conditions in the field (x, y coordinates and z heights of 944 cavities available for roosts). This simplified habitat setting was considered sufficient because cavity density and height are the primary determining factors in roost-site selection of tree-dwelling bats 6,10,11,25,54 . In a hexagonal grid divided into 37 equal cells, density of cavities ranged from 8 to 92 per a cell ( Fig.…”

“…Groups roosting in tree cavities in Gavurky were found by radio-tracking or by search during dawn swarming with the help of a bat detector, and they were censused at evening emergence, supplemented by harp-trapping and individual banding. During long-term field observation from 2003 to 2014, we collected data on spatial distribution of bats’ roosts, group size, elevation of cavity entrance above the ground (hereafter cavity or roost height) and distance travelled during group roost switching (for details see 35 , 36 , 51 – 54 ). All methods were carried out in accordance with relevant guidelines and regulations.…”

“…In general, this species prefers higher tree roosts 10 , 11 , 25 , 54 . On the other hand, it should avoid roosts infested by parasites 18 , 26 ; therefore, excrements were used as a proxy of the load of parasites associated with guano 28 .…”