Investigating trade-offs in Strength, Skill and Vigour in Pagurus Bernhardus

Abstract

The ability to win contests is vital for securing the valuable resources individuals
need for survival, or in some cases to secure mating opportunities. Therefore,
fighting can have a strong influence over fitness, and much research has been
carried out to identify and understand the traits influencing fighting ability, also
known as resource holding potential (RHP). RHP has been found to be
influenced by a wide range of factors including morphology, physiology, vigour
and, more recently, skill. These factors are typically analysed in isolation from
one another, so as to identify the individual impact of each trait. However, to
gain a more comprehensive understanding of RHP we would benefit from
identifying how these different traits potentially interact and trade-off with one
another to determine overall RHP. Strength is relatively under-researched in the
context of fighting, therefore we know very little about how it affects fighting
behaviour or other RHP traits. Using the European hermit crab Pagurus
bernhardus, we investigated the relationship between three RHP traits:
strength, vigour and skill. We identified a potential trade-off between strength
and skill, indicating that individuals might have to choose between different
agonistic strategies. In contrast, vigour appears to be unrelated to strength,
suggesting that the two factors are influenced by independent sets of traits. The
near universal investment in vigorous fighting amongst the majority of
individuals, while strength and skill appear to trade-off (perhaps in competition
for limited energetic budget) implies that some RHP traits might be considered
more important than others and thus receive greater investment. We may have
also identified a potential measure of efficiency, that being gripping style, where
some individuals appear to apply their strength in shorter bursts of force, which
might better suit fighting which involves brief periods of agonistic behaviour, and
prolonged rests. In conclusion, our results indicate that there are numerous
complex links between different RHP traits which in some cases force trade offs. Therefore, we should make attempts to study fighting behaviour more
holistically, if possible, rather than considering them each in isolation.

Date of Award	2024
Original language	English
Supervisor	Mark Briffa (Director of Studies (First Supervisor)) & Sarah Lane (Other Supervisor)