social learning

Project: Social learning during ontogeny
D
o pups follow their mothers on first foraging flights?

Following their mothers during first foraging flights should represent a valuable option for juveniles to socially learn about foraging, e.g. where to find resource rich foraging patches. However, explicit tests are scarce, and evidence for communal or independent foraging of mother-pup pairs in some species is mainly based on partially anecdotal reports with rather vague methods.

In this project, we use a novel approach to investigate the early foraging behavior of free flying flower-visiting bats in the National Park Santa Rosa in Costa Rica. We test whether recently volant, but still nursed pups perform first foraging flights alone, indicating a rather individual learning strategy, or whether pups follow their mothers, which would enable pups to learn socially. For that, we use an experimental setup of inexhaustible artificial flowers in the forest nearby the bats’ roost. Each flower comprises an RFID reading system that allows us to precisely record individual visits of RFID tagged mothers and their pups.

captive Glossophaga mother-pup pairs
A group of ten temporarily captive mother-pup pairs shortly before they were equipped with RFID transponders and released to the outdoor experiment. At this time, pups were still nursed with milk, but were already volant and feeding on nectar. (mothers: brown fur, pups: grey fur).
RFID flowers
Artificial flowers with RFID reading system were mounted in the vicinity of the day-roost.
RFID flower in the outdoor experiment
One RFID flower mounted in the forest close to the day-roost. The big tree in the background on the right is a flowering bat-pollinated Pachira quinata (Malvaceae).

Project: Social learning during ontogeny
Do pups use maternal mouth-to-mouth feeding behavior to learn about food cues?

Rose A, Wöhl S, Bechler J, Tschapka M, Knörnschild M (2019) Maternal mouth-to-mouth feeding behaviour in flower-visiting bats, but no experimental evidence for transmitted dietary preferences. Behavioural Processes, 165:29-35

In addition to breast milk, several mammals feed their offspring with primary food items. This provisioning can offer both energetic and informational benefits: young might use parentally provided food as a source of nutrients, but also as a valuable option to socially learn about adults’ food. For bats, there are only very few and partially anecdotal reports of adults feeding their pups with primary food, and there is also a lack of information about social learning processes during ontogeny. In the present study, we provide experimental evidence that lactating flower-visiting bats (Glossophaga soricina) provide regurgitated nectar via mouth-to-mouth feeding behaviour to their pups. After licking at their mothers’ slightly opened mouth, pups defecated a marker substance that was exclusively available in the mothers’ nectar diet.  We additionally investigated associated informational benefits by testing for a social transmission of dietary preferences. We experimentally induced a dietary preference for specifically flavoured nectars to mothers with non-volant pups. Subsequently, after pups became volant, we tested their dietary preferences in a choice experiment. However, we found no experimental evidence that pups adopted the preferences of their mothers.

Glossophaga mouth-to-mouth feeding
Pup (dark fur) licks reurgiated nectar out of the opened mouth of its mother.

 

Videos on maternal mouth-to-mouth feeding behavior can be found here.

 


Social learning in adults
Learning where to feed

Rose A, Kolar M, Tschapka M, Knörnschild M (2016) Learning where to feed: The use of social information in flower-visiting Pallas’ long-tongued bats (Glossophaga soricina). Animal Cognition, 19:251-262

In an experiment with captive G. soricina at the University of Ulm, we demonstrated that flower‐visiting bats (Glossophaga soricina) readily use social information gained from interactions with knowledgeable conspecifics to find rewarding flowers in an artificial flower‐field. This social transmission of knowledge reduces the high energetic costs of searching for flowers and thus constitutes an attractive alternative to individual (i.e. trial‐and‐error based) learning in foraging bats.

In the experiment, focal bats had to find one rewarding flower among 15 unrewarding flowers in three different situations:

(1) trial-and-error situation (focal bat alone): The naive focal bat (marked by a reflective stripe) has to apply a trial-and-error based individual learning strategy to find the rewarding flower position (green circle) among 15 unrewarding flowers.

(2) social facilitation situation (focal bat + naive conspecific): the focal bat (marked by a reflective stripe) and  a naive conspecific searching for the rewarding flower position (green circle)

(3) social transmission situation (focal bat + demonstrator bat): Hovering flight of a trained demonstrator bat attracts focal bat (marked by a reflective tape) to the rewarding flower (green circle). The focal bat is hanging at the ceiling, but performing a flower approach towards the rewarding flower after the demonstrator bat was feeding. The focal bat first tries to feed from the rear side, than landing at the rewarding flower and finally feeding while hovering in front of the flower. The focal bat had performed several unsuccessful feeding attempts at unrewarding flowers before.

Search effort (i.e. number of unsuccessful flower visits) was significantly reduced in the social transmission situation. Focal bats socially learned about the rewarding flower position most likely as a result of local enhancement…