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Home > Research > Understanding Biodiversity: Evolutionary and Behavioural Ecology > Cooperation and population dynamics in the Sociable Weaver
Current Research Programmes

Cooperation and population dynamics in the Sociable Weaver

The elaborate social structure and cooperative behaviour of Sociable Weavers Philetairus socius in their large nesting colonies make them an ideal model to study the effects of environmental and social factors on population dynamics and the benefits and costs of cooperation. We have been gathering detailed data on cooperative breeding for seven years, and our long-term demographic data spans over 20 years.

The long-term nature of this project affords unique data and insights to understand the evolution of cooperation and the mechanisms that allow Sociable Weavers to persist. Simultaneously, the demographic data allows examination of the factors affecting population dynamics in relation to environmental change.

Activities in 2016

  • Post-doc Sophie Lardy concluded a demanding experiment where the cost of helping was artificially manipulated. Sophie also collected blood and plasma samples for over 300 individuals. Her Claude Leon Post-doctoral fellowship at the Fitz ended in August 2016, and she is analysing her data through a Post-doctoral fellowship based at the CNRS in Montpellier, France.
  • Analyses of oxidative stress and telomere length were conducted in collaboration with François Criscuolo from CNRS Strasbourg, France.
  • PhD student André Ferreira and Post-doc Arnaud Tognetti conducted field trials for experiments to be conducted in the 2017 breeding season. André will investigate the reliability of cooperative behaviour and the social benefits of cooperating. To measure social benefits we will use social networks in collaboration with Damien Farine (Max Planck, Germany). Arnaud will investigate whether helping behaviour may be used as a signal to attract mates. He will test whether helpers change their behaviour in relation to changes in the ‘audience’, i.e. the individuals that witness cooperative behaviours. The change in audience will be mimicked by broadcasting calls from males and females. We started collaboration with acoustics expert Fanny Rybak (U. Orsay, France) to assist with this project.
  • Janine Greuel started an MSc project working with Bryan Maritz (UWC) to study the ecology of Boomslangs Dyspholidus typus and Cape Cobras Naja nivea and how they interact with Sociable Weaver colonies.
  • The collaboration with Ben Hatchwell and René van Dijk (University of Sheffield, UK) has found inbreeding avoidance in Sociable Weavers. An ongoing experimental study aims to understand the mechanisms of kin recognition underpinning this inbreeding avoidance.
  • To improve data collection and storage, we are creating a standardized database that will integrate capture-recapture, reproduction and cooperation data. Franck Theron was hired to develop and run the database, and Jerémy Tornos was appointed a short-term contract to develop a tablet interface for data collection in the field.

Highlights

  • Two major grants were obtained in 2016 from the Portuguese (FCT) and French (ANR) national research agencies to investigate whether cooperation provides direct benefits to individuals, in addition to those obtained through helping close kin. A new PhD student, and two Post-docs have joined the project under these grants.
  • CB MSc student Kyle Lloyd used a 5-year experimental exclusion of snakes from specific colonies to confirm the negative role of nest predation on reproductive output and population trends (snakes take ca 70% of eggs and chicks). Warm winters also benefit the weavers. For example, in 2016 a relatively warm winter and late rains allowed the weavers to breed continuously through winter into the following summer. Surprisingly though, Kyle found that under the increased aridity predicted by the climate models, this population would decline, even if under continuous predator exclusion and warmer winters. To further understand the role of snakes in this ecosystem we have initiated a collaboration with herpetologist Bryan Maritz (UWC).
  • MSc student Rita Fortuna (U. Porto) graduated in 2016 with a study on begging behaviour. Previously we had shown experimentally that chicks produced by females with helpers begged less than those from females without helpers, probably because females put less hormones in their eggs when they have helpers. Rita demonstrated that males, females and helpers all respond similarly to begging, but parents receive higher-frequency begging calls than helpers.
  • MSc student Liliana Silva (U. Porto) graduated in 2016 with a study on the physiological costs of helping. Previous work revealed fitness benefits of dominance in terms of access to resources and higher numbers of helpers. Liliana tested whether dominance also has costs, using oxidative stress as a proxy. Interestingly, she found costs for females but not males, revealing an unexpected pattern, which might arise because of the reduced access to resources experienced by females coupled with a higher cost of reproduction.
  • MSc student Rebecca Goldberg (U. Sheffield) graduated in 2016 with a thesis on kin recognition and inbreeding avoidance.
  • A paper by former Fitz Post-doc, Matthieu Paquet, illustrating the thermoregulatory benefits of communal roosting was published in Journal of Avian Biology, and was picked as the Editor's choice.
  • The Sociable Weaver was chosen as BirdLife SA bird of the year.
  • Four new collaborations were initiated: Bryan Maritz (snake ecology); Damien Farine (social networks), Fanny Rybak (acoustics), François Criusculo (telomeres).

Impact of the project

The long-term nature of this project affords unique data and insights to understand the evolution of cooperation and the mechanisms that allow Sociable Weavers to persist. Simultaneously, the demographic data allows examination of the factors affecting population dynamics in relation to environmental change.

Key co-sponsors

FCT, Portugal; French Research Agency; ANR, France; DST-NRF Centre of Excellence grant; Marie Curie-IRSES, EU.

Research team

Dr Rita Covas (FIAO, UCT and CIBIO, U. Porto)
Dr Claire Doutrelant (FIAO, UCT and CNRS, France)
Dr Sophie Lardy (FIAO, UCT and CNRS)
Dr Arnaud Tognetti (U. Toulouse)

Students: André Ferreira (PhD, U. Porto); Rita Fortuna (MSc, U. Porto); Rebecca Goldberg (MSc, U. Sheffield); Janine Greuel (MSc, UWC), Liliana Silva (MSc, U. Porto); Kyle Lloyd (CB MSc, UCT);

Research Assistants: Rita Leal, Thomas Pagnon, Maxime Passerault, Hugo Pereira, Franck Theron.