When more is not merrier: using wild population dynamics to understand the effect of density on ex situ seahorse mating behaviors

Seahorses are one of the most iconic examples of a monogamous species in the animal kingdom. Documenting monogamous behaviors of seahorses have proven to be quite complicated to study in the wild because of their low population densities and cryptic habits. Another challenge involves interpreting these behaviors in captivity because recreating realistic densities of wild populations in the laboratory can be difficult due to their patchy distributions. This study investigates the relationship between stocking density and mating and competitive behavior from the context of the field biology of the dwarf seahorse, Hippocampus zosterae (Jordan & Gilbert). Animals were housed in 38 liter tanks at a range of densities and sex ratios (from 2-8 animals per tank), and their reproductive and other social behaviors were monitored from tank introduction through copulation. At low tank densities and even sex ratios but comparatively high field densities, activity level in trials was low. A highe...