Cooperation among Norway rats: The importance of visual cues for reciprocal cooperation, and the role of coercion
Publisher DOI
Abstract
Some animals reciprocate help, but the underlying proximate mecha-
nisms are largely unclear. Norway rats (Rattus norvegicus) have been
shown to cooperate in a variant of the iterated prisoner’s dilemma
paradigm, yet it is unknown which sensory modalities they use. Visual
information is often implicitly assumed to play a major role in social inter-
actions, but primarily nocturnal species such as Norway rats may rely on
different cues when deciding to reciprocate received help. We used an
instrumental cooperative task to compare the test rats’ propensity to recip-
rocate received help between two experimental conditions, with and
without visual information exchange between social partners. Our results
show that visual information is not required for reciprocal cooperation
among social partners because even when it was lacking, test rats
provided food significantly earlier to partners that had helped them to
obtain food before than to those that had not done so. The mean decision
speed did not differ between the two experimental conditions, with or
without visual information. Social partners sometimes showed aggressive
behaviour towards focal test individuals. When including this in the anal-
yses to assess the possible role of aggression as a trigger of cooperation,
aggression received from cooperators apparently reduced the cooperation
propensity, whereas aggression received from defectors increased it.
Hence, in addition to reciprocity, coercion seems to provide additional
means to generate altruistic help in Norway rats.
nisms are largely unclear. Norway rats (Rattus norvegicus) have been
shown to cooperate in a variant of the iterated prisoner’s dilemma
paradigm, yet it is unknown which sensory modalities they use. Visual
information is often implicitly assumed to play a major role in social inter-
actions, but primarily nocturnal species such as Norway rats may rely on
different cues when deciding to reciprocate received help. We used an
instrumental cooperative task to compare the test rats’ propensity to recip-
rocate received help between two experimental conditions, with and
without visual information exchange between social partners. Our results
show that visual information is not required for reciprocal cooperation
among social partners because even when it was lacking, test rats
provided food significantly earlier to partners that had helped them to
obtain food before than to those that had not done so. The mean decision
speed did not differ between the two experimental conditions, with or
without visual information. Social partners sometimes showed aggressive
behaviour towards focal test individuals. When including this in the anal-
yses to assess the possible role of aggression as a trigger of cooperation,
aggression received from cooperators apparently reduced the cooperation
propensity, whereas aggression received from defectors increased it.
Hence, in addition to reciprocity, coercion seems to provide additional
means to generate altruistic help in Norway rats.
Date Issued
2015
Publication Type
Article
Subject(s)
Language(s)
en
Additional Credits
Journal
Ethology
Publisher
Wiley-Blackwell
ISSN
0179-1613
Access(Rights)
restricted