Exceptional natal dispersal patterns – a valuable opportunity to study the proposed evolutionary pressures
Natal dispersal is usually sex-biased with female-biased natal dispersal prevailing in the majority of bird species while male-biased natal dispersal prevails in mammals. The main discussed evolutionary forces shaping natal dispersal patterns include the avoidance of inbreeding, the avoidance of local mate competition, the avoidance of local resource competition and kin cooperation. Though, there is still much disagreement about the relative importance of these ultimate causes for sex-biased natal dispersal. Studying exceptions to general patterns of natal dispersal, e.g. female-biased natal dispersal in mammals as we found in Rhynchonycteris naso, provides a valuable opportunity to test the validity and relative importance of proposed evolutionary pressures.
Exceptional natal dispersal patterns – a valuable opportunity to study the proposed evolutionary pressures
Natal dispersal is usually sex-biased with female-biased natal dispersal prevailing in the majority of bird species while male-biased natal dispersal prevails in mammals. The main discussed evolutionary forces shaping natal dispersal patterns include the avoidance of inbreeding, the avoidance of local mate competition, the avoidance of local resource competition and kin cooperation. Though, there is still much disagreement about the relative importance of these ultimate causes for sex-biased natal dispersal. Studying exceptions to general patterns of natal dispersal, e.g. female-biased natal dispersal in mammals as we found in Rhynchonycteris naso, provides a valuable opportunity to test the validity and relative importance of proposed evolutionary pressures.
The influence of animal personality on male reproductive tactics of social mammals
The reproductive tactic plays a significant role in the individual fitness and can be regarded as key factor in the lives of organisms. But what influences an individual’s reproductive tactic? Besides well-studied physical and morphological traits (e.g., size, strength, weapons, ornaments), individuals also often differ consistently in their way of responding to particular situations – i.e. they possess individual personalities. Such individual personalities can be found across a wide range of animal taxa, but their effects on the acquisition of a specific reproductive tactic, and the resulting individual fitness are poorly understood.
Project aim
This project will investigate how and to which degree personality may promote variation in male reproductive tactics. Further, the males’ reproductive behaviour and resulting success will be assessed in a seasonally changing environment to investigate the adaptive character of male personality and the linked RT in heterogeneous environments. Finally, the heritability of personality traits will be explored to determine the genetic component of the traits – a prerequisite for selection to act on the traits.
< This foto by PhD student Andreas Rose (University of Ulm) shows three G. soricina competing for the access to a nectar source. This artificial flower was designed and build by Rose. The foraging behaviour by G. soricina builds a unique opportunity experimental setups to study the role of food resource-defence behaviour in relation to reproductive tactics and individual personality.
Approach and methods
In order to achieve the described aims, bats represent promising study objects. Especially in the tropics, several bat species are known to form long-lasting stable social groups with derived mating systems and individual reproductive roles. Often, they permanently use the same shelter (i.e. roost), where they can be found during the day. The Neotropical nectar-drinking Pallas’s long-tonged bat (Glossophaga soricina) represents a particularly promising species as previous studies suggest that males of this group-living species pursue alternative reproductive tactics (defence of a specific site within their roost vs. defence of flowers outside the roost). Moreover, there is – so far unique among bats – evidence for individual personality types in the context of foraging. Based on this, in the proposed project members of six free-ranging G. soricina-groups will be tested for individual personality in the roosting and foraging context in four different traits: boldness, exploration propensity, neophilia, and flexibility. The results of these standardised tests will be combined with detailed studies on reproductive behaviour as well as the resulting individual male reproductive success in mating seasons with distinct environmental conditions (dry vs. wet mating season). Genetic relatedness analyses will allow reconstructing detailed pedigrees of the six study groups – the basis for calculating the degree of heritability of the assessed personality traits. Besides behavioural monitoring within the roosts by observations of individually tagged bats, recent developments in biologging (i.e. automated capture of behavioural interactions by proximity sensors) allow for the hitherto impossible detection of individual interactions of these highly mobile animals outside their roosts. Overall, this project builds a rare possibility to advance our understanding of how and to which degree personality may influence individual reproductive behaviour of males in highly social group-living animals.
G. soricina feeding on the flower of a calabash tree (Crescentia alata, Bignoniaceae) (Santa Rosa, Costa Rica).