Our long-term project at Benfontein Reserve uses the aptly named Sociable Weaver Philetairus socius to study questions about the ecology and evolution of social behaviour. We have continued our work investigating whether sociality contributes to buffer against the extremes of the Kalahari climate, and recent work has been investigating how social associations form and persist but is also revealing a dark side of social living. 

The Sociable Weavers at Benfontein enjoyed a long breeding season, which lasted until May and saw 332 chicks fledging. Nonetheless, our yearly captures in September revealed that the population has barely increased. Unfortunately, that is not entirely surprising, given new survival analyses conducted by postdoctoral fellow Sophie Dupont, which used data going back to 1993 and showed that juvenile sociable weavers have highly variable but generally low survival. These results demonstrate once again the importance of long-term studies and how this data collection effort, led by Rita Covas and Claire Doutrelant, allows us to describe some key demographic parameters. To further understand the factors that might have a negative impact on population outcomes, Conservation Biology MSc student Niels Zwartjes started a project investigating whether high temperatures impact nestling growth and whether having helpers at the nest can counter these possible negative effects. 

Much of the work conducted over the last year has taken a deep look at the social associations in this species: how they form, whether they are stable through time and what the benefits of these social associations are. PhD student Babette Fourie showed that Sociable Weaver social associations are remarkably persistent through time, but also that new associations can form if individuals from different groups are encouraged to spend time together. In a fascinating experiment, Babette manipulated familiarity at artificial feeders and the results showed that this fostered new social associations among these birds. Having a high number of strong social associations is important, as shown by postdoctoral researcher Gabriel Munar, who found that birds with strong bonds have higher survival and higher reproductive success. Postdoctoral fellow Jorge Campa has found that Sociable Weavers are remarkable in their capacity to change flexibly between breeding and helper roles – up to 15 times for one individual! To study behaviours such as helping at the nest, it is essential to be able to identify individual birds and their behaviour. Liliana Silva has been developing AI-based models for automatic identification of behaviours and individual colour combinations, while former PhD student Nicolas Silva developed a deep-learning–based method capable of detecting sexual dimorphism in sexually monomorphic Sociable Weavers. 

PhD student Marta Marmelo carried out fieldwork at Benfontein and Tswalu to study mobbing in Sociable Weavers by presenting models of snakes and Pygmy Falcons Polihierax semitorquatus. She identified vocalisations that are produced in the presence of these predators and possible geographical differences in some vocalisations.

Activities in 2025
  • Postdoc Sophie Dupont used long-term data going back to 1993 to show that adult Sociable Weavers have relatively stable survival rates, while juvenile survival rates are highly variable but generally low. Both groups were severely affected by the destructive September 2021 fire.
  • Conservation Biology MSc student Niels Zwartjes is investigating the effects of heat on nestling growth and whether helpers at the nest may buffer against possible negative effects.
  • PhD student Babette Fourie analysed the results of an experiment that manipulated feeding behaviour and fostered new social associations. A manuscript was submitted for publication.
  • PhD student Marta Marmelo found that some Sociable Weaver vocalisations are produced preferentially in the presence of predators, as well as possible geographical differences in calls.
  • Postdoc Gabriel Munar produced two manuscripts describing the association between the level of sociality of an individual and the key fitness parameters survival and reproductive success.
  • Gabriel and research technicians Franck Théron and David Delguere and engineer Killian Pareilleux upgraded the feeding stations that automatically record feeding associations.
  • Postdoc Jorge Campa submitted a manuscript describing high flexibility in switching between breeder and helper roles in this species, an unusual characteristic in cooperative breeders.
  • Field manager Sara Piquet has begun a PhD position in the project. She will be studying whether early life conditions influence individual propensity to be more or less cooperative in adult life. 
Highlights
  • Babette Fourie presented at the ASAB Spring Conference in Liverpool, UK, the results of a fascinating experiment that manipulated feeding associations and fostered new social bonds.
  • Rita Covas was invited to deliver the Dobberke Lecture at the Netherlands Society for Behavioural Biology Meeting in November, where she presented the Sociable Weaver research.
  • Marta Marmelo gave a seminar at the Fitz in October describing her work on mobbing calls.
  • Former PhD student Nicolas Silva led the publication of a deep-learning–based approach that can detect sexual dimorphism in sexually monomorphic Sociable Weavers.
  • Former postdoc Pietro D’Amelio published a paper investigating whether the presence of novel individuals influenced nestling provisioning behaviour in Sociable Weavers.
  • The long-term data from this population at Benfontein forms part of the integrative, peer-reviewed, open-source Cooperative Breeding Database, which includes data on > 300 species. 
Impact of the project

The long-term nature of this project allows unique insights into the evolution of cooperation and the mechanisms that allow it to persist. The demographic data allow for examination of the factors affecting population dynamics, provide a baseline against which to study environmental change and natural disasters (which are increasing in frequency under climate change), and provide insight into whether and how sociality mediates the response to a changing environment.

Key co-supporters
European Research Council (ERC); Marie Curie – Staff Exchange (EU); French Research Agency (ANR); Portuguese Foundation for Science and Technology CNRS–SEE-Life label (France), OSU-OREME (France).

Research team 2025
Team leaders and collaborators:
Dr Rita Covas (FIAO, UCT / CIBIO, U. Porto)
Dr Claire Doutrelant (CNRS, France)
Liliana Silva (CIBIO, U. Porto)
Franck Théron (CIBIO, U. Porto)
Dr Sophie Dupont (U. Montpellier, CNRS, France)
Dr Jorge Campa (CIBIO, U. Porto)
Dr Gabriel Munar (CIBIO, U. Porto)
Dr André Ferreira (U. Zurich, Switzerland)
Dr Fanny Rybak (U. Paris-Sud, France)

Students:
Babette Fourie (PhD, U. Porto); Marta Marmelo (PhD, U. Porto); Sara Piquet (PhD, U. Porto); Niels Zwartjes (MSc, FIAO, UCT), Hypolite Dupas (Internship, U. Montpellier), Lea Geng (MSc, U. Paris Sud)

Research Assistants:
Paulo Ditzel, Marine Hoareau, Lewis Heriot, Alex Alaman, Sara Piquet, Natacha Planque, Kiley van Meer, Killian Pareilleux, Khaveli Adam