‘Solo datasets’: unexpected behavioural patterns uncovered by acoustic monitoring of single individuals

Abstract

A holistic understanding of the life-history strategies of marine populations is often hindered by complex population dynamics, exacerbated by an intricate movement ecology across their life history (Nathan et al. 2008; Parsons et al. 2008; Jeltsch et al. 2013). Movement patterns and spatial ecology can vary spatially and temporally for different reasons, mainly related to the organism’s life history and environmental variability (Abecasis et al. 2009, 2013; Afonso et al. 2009). Changes in spatial use and movement can occur daily when visiting feeding grounds or avoiding predators, or seasonally, when sexually mature individuals migrate to spawning/breeding grounds (Kozakiewicz 1995; Sundström et al. 2001). However, observed shifts in spatial use and movement patterns, as a result of behavioural plasticity, may also vary greatly from one individual to another of the same species and/or population (Afonso et al. 2009). Further, ontogeny can also play an important role and explain a possible change in individual spatial variation. Noticeable differences in the behaviour and movements of mature and immature individuals have been documented in various marine organisms (Lowe et al. 1996; Lecchini and Galzin 2005). Permanent habitat shifts have been associated with ontogenesis in pigeye sharks (Carcharhinus amboinensis), moving from inshore to offshore areas after reaching maturity (Knip et al. 2011). Hence, a relevant debate lies in the implications of ‘solo datasets’ and the potential pertinence of the patterns an individual dataset could uncover. Data deficiency can be the primary barrier to efficient marine conservation and management, and while longterm species-specific data are often lacking (Broderick 2015), it appears worthwhile to investigate patterns exhibited by single individuals as a baseline to address further research projects more thoroughly. Relatively, long-term monitoring of a unique specimen can reveal extraordinary, previously unexpected behaviours. For instance, using a ‘solo dataset’ from a scalloped hammerhead shark, Sphyrna lewini, Spaet et al. (2017)