—- By Gwylim S. Blackburn & Wayne P. Maddison—-
Animals reveal a lot about their lives simply by the way that they behave. When observed in the wild, they also offer insights to the function of behaviours in a natural context. Capturing these insights just requires a little patience, and attention to the right details.
In a recent study printed in the journal Behaviour, we set out to document Habronattus americanus jumping spider behaviors that would shed light on their ‘mating strategies’—the tactics used by females and males to acquire mates. Specifically, we wanted to know if males show off their flashy displays only to females or also compete directly with each other, if they invest heavily in mate search, and if females are choosy when deciding who to mate with.
To pursue these issues, we followed 41 adults for up to 30 minutes each, and we also staged interactions between an additional 36 male-female pairs, in natural habitat.
The behaviours of both sexes pointed quite strongly to indirect male competition for choosy females. Males did not display to (or fight with) each other. Instead, they travelled far and wide, eating nothing but displaying to every female they met. Females, on the other hand, focused on hunting rather than travel, and they almost never permitted copulation despite the vigorous courtship efforts of males.
Collectively, these behaviours supply deeper lessons than their individual functions; they also indicate how natural selection might shape several of the traits involved. In particular, our findings suggest that female mate choice may be the key source of selection favouring the evolution of male display traits.
The apparently high investment by males in mate search also represents a potential factor shaping female mate preferences. In a variety of other species, mate search costs have been shown to provide a way for females to judge the quality of prospective mates. This is because males who are able to pay those costs while still producing an impressive display can make better fathers (e.g., by providing better parental care, or by passing along advantageous genes to their offspring). To determine if this is the case in H. americanus, further research will be needed to see how male condition is linked to the quality of their displays and the success of their offspring.
The Habronattus jumping spiders are famous for their stunning array of male displays. It would be fascinating to know how mating strategies, and the natural surroundings in which they unfold, have influenced this diversity. Behavioural observations of different species in the wild will be essential for getting at this question.
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