Socially induced ovulation synchrony and its effect on seabird population dynamics

Abstract

Spontaneous oscillator synchrony is a form of self-organization in which populations of interacting oscillators ultimately cycle together. This phenomenon occurs in a wide range of physical and biological systems. In rats and humans, oestrous/menstrual cycles synchronize through social stimulation with pheromones acting as synchronizing signals. In previous work, we showed that glaucous-winged gulls (Larus glaucescens) can lay eggs synchronously on an every-other-day schedule, and that synchrony increases with colony density. We posed a discrete-time mathematical model for reproduction during the breeding season based on the hypothesis that pre-ovulatory luteinizing hormone surges synchronize by means of visual, auditory and/or olfactory cues. Here, we extend the seasonal model in order to investigate the effect of ovulation synchrony on population dynamics across reproductive seasons. We show that socially stimulated ovulation synchrony can enhance total population size and allow the population to persist at lower birth rates than would otherwise be possible.

A juvenile–adult population model: climate change, cannibalism, reproductive synchrony, and strong Allee effects

“…Another mechanism that can cause reproductive synchrony is the prey saturation effect in the cannibalism model (16)- (19). This is illustrated in the example simulations shown in Figure 3.…”

“…For gulls however the cycling is in days and the maturation period is in years. A model that allows for this difference in time scales is given in [19].…”

“…The Fraser Darling Effect [12] states that seasonal reproductive synchrony in colonial birds may confer a selective advantage by means of predator satiation. Similarly, Henson et al [19] hypothesized that every-otherday ovulation synchrony in gulls may be a response that confers a selective advantage by means of cannibal satiation.…”

A note on the onset of synchrony in avian ovulation cycles

“…0 is a surrogate for colony density and controls the strength of the delay mechanism. As c increases from zero, the x-and y-components of the solution begin to oscillate with period 2 [2]. Because the number of birds in the x-class on a given day is the number of ovulations occurring that day, the biological interpretation of the oscillating solution is every-other-day ovulation synchrony.…”

“…Model (1) by itself is not a population model, but rather describes ovulation dynamics within the breeding season. All solutions of model (1) approach zero [2]; that is, all birds eventually begin ovulating, complete their clutches and begin incubation. Thus, ovulation synchrony is a transient phenomenon in model (1).…”