Nührenberg, Paul


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On the importance of defendable resources for social evolution : Applying new techniques to a long-standing question

2021-10, Jungwirth, Arne, Nührenberg, Paul, Jordan, Alex

Cooperative behaviour often co-occurs with the defence of key resources, typically in the form of a breeding site or territory communally exploited by a group of cooperating individuals. Nevertheless, not all animals that defend resources evolve advanced forms of cooperation and sociality—many non-cooperative species occupy resources that do not differ in obvious ways from those inhabited by cooperative species. A key question is thus whether cooperation confers more subtle benefits, for example by allowing access to higher quality resources through competitive exclusion of less social rivals. In other words, it is not clear whether defendable resources are a necessary precondition for sociality or whether they also contribute to the maintenance and enhancement of cooperative societies. Here, we highlight how advances in imaging technology, machine-learning, and environmental reconstruction enable the collection of behavioural and ecological data in unparalleled quantity and quality to address this question. These new techniques are especially suited to compare small-scale differences in resource use between cooperative and non-cooperative species that share a general habitat and have similar ecologies. The lamprologine cichlids of Lake Tanganyika are a prominent example of such a system and Michael Taborsky's pioneering work on this group has done much to promote these fishes as models of social evolution. We show that habitat features indicative of increased resource quality, namely increased stone cover, are indeed associated with the distribution of cooperative cichlids—at least where these resources are relatively scarce. We thus support a point Michael Taborsky made in 1981: the evolution of cooperative behaviour among cichlids is tied to their close association with a crucial resource, the substrate in which they hide and breed. In the future, the techniques we introduce here will allow to also investigate whether this substrate is indeed more than just the necessary precondition for cooperation among fishes; in addition, they will likely find application in a wide range of research fields interested in the interplay between biotic and abiotic environmental factors.


Behavioral traits that define social dominance are the same that reduce social influence in a consensus task

2020, Rodriguez-Santiago, Mariana, Nührenberg, Paul, Derry, James, Deussen, Oliver, Francisco, Fritz A., Garrison, Linda Karen, Garza, Sylvia F., Hofmann, Hans A., Jordan, Alex

The attributes allowing individuals to attain positions of social power and dominance are common across many vertebrate social systems: aggression, intimidation, and coercion. These traits may be associated with influence, but may also be socially aversive, and thereby decrease social influence of dominant individuals. Using a social cichlid fish, we show that dominant males are aggressive, socially central, and influence group movement. Yet, dominant males are poor effectors of consensus in a more sophisticated association task compared with passive, socially peripheral subordinate males. These influential, subordinate males possess behavioral traits opposite of those generally associated with dominance, suggesting that the link between social dominance and social influence is context dependent, and behavioral traits of dominant males impede group consensus formation.


Environmental Reconstruction and Tracking as Methods to Explore Social Interactions in Marine Environments : A Test Case With the Mediterranean Rainbow Wrasse Coris julis

2021-07-23, Goverts, Zoe, Nührenberg, Paul, Jordan, Alex

A key aspect of understanding social interactions in marine animals is determining whether individuals freely interact in fission-fusion groups, or have spatially structured interactions, for example territories or home ranges. Territoriality can influence access to mates, food resources, or shelter sites, and may also impact conservation efforts, as the delineation of marine protected areas relies on knowledge of home ranges and movement patterns. However, accurately determining distribution and movement is challenging for many marine species, especially small and medium species, which cannot carry beacons or tags to automatically measure movement, and are also difficult for human observers to accurately follow. Yet these smaller species comprise the bulk of near-shore assemblages, and are essential conservation targets. As such, novel solutions for monitoring movement and behavior are required. Here we use a combination of tracking and environmental reconstruction to explore territoriality, aggression, and navigation in a small marine fish, explicitly applying this technique to questions of sociality in the marine environment. We use the Mediterranean Rainbow Wrasse, Coris julis, as a test case, but this approach can be extended to many other species and contexts. In contrast with previous reports for this species, we find that during our observation period, female C. julis occupy consistent territories over sand patches, and that they defend these territories against same-sex conspecifics. Displacement experiments revealed two further important social behavioral traits – first that displaced individuals were able to navigate back to their territory, avoiding almost all other female territories as they returned. Second that when displaced fish approached the territories of others, residents of these territories were often aggressive to the non-neighboring fish, in contrast with our observations of low aggression counts toward their natural neighbors. Resident fish therefore appear to show differing levels of aggressiveness depending on their social relationship with same-sex conspecifics. Overall, these results suggest a sophisticated degree of social behavior in this marine wrasse, dependent on social and structural environment, but which can only effectively be revealed by state-of-the-art tracking and environment reconstruction techniques.


High-resolution, non-invasive animal tracking and reconstruction of local environment in aquatic ecosystems

2020, Francisco, Fritz A., Nührenberg, Paul, Jordan, Alex

Acquiring high resolution quantitative behavioural data underwater often involves installation of costly infrastructure, or capture and manipulation of animals. Aquatic movement ecology can therefore be limited in taxonomic range and ecological coverage.

Here we present a novel deep-learning based, multi-individual tracking approach, which incorporates Structure-from-Motion in order to determine the 3D location, body position and the visual environment of every recorded individual. The application is based on low-cost cameras and does not require the animals to be confined, manipulated, or handled in any way.

Using this approach, single individuals, small heterospecific groups and schools of fish were tracked in freshwater and marine environments of varying complexity. Positional tracking errors as low as 1.09 ± 0.47 cm (RSME) in underwater areas up to 500 m2 were recorded.

This cost-effective and open-source framework allows the analysis of animal behaviour in aquatic systems at an unprecedented resolution. Implementing this versatile approach, quantitative behavioural analysis can be employed in a wide range of natural contexts, vastly expanding our potential for examining non-model systems and species.

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Female-female conflict is higher during periods of parental care in a group-living cichlid fish

2021, Bose, Aneesh P. H., Nührenberg, Paul, Jordan, Alex

Parental care can be associated with novel or altered social relationships with conspecifics, yet little is known about how the broader structure of the social environment is modulated by individuals caring for dependent offspring. Here, we compared the social environments of breeding groups in which dependent offspring were either present or absent. We conducted a field study with Neolamprologus multifasciatus, a group-living cichlid fish endemic to Lake Tanganyika, in which females provide direct care for their offspring within a group's territory. We used two methods to characterize the social environments in each group: (1) behavioural scoring to quantify the interactions among all group members and (2) automated, computer-assisted, visual detection to track the movements of fish on their territories. We found that relative to groups without offspring, groups with dependent offspring showed heightened conflict among females, as well as appreciable contests between dominant males and noncaregiving females. Patterns of space use revealed that territories comprise distinct, female-held subterritories, and although caregiving females used wider spaces than noncaregiving females, their subterritory areas remained largely nonoverlapping. By combining two complementary approaches for characterizing the social environment we were able to show how periods of parental care can be associated with marked differences in the makeup of breeding groups' social environments.