Identifying Diurnal Foraging Habitat of Endangered Hawaiian Monk Seals Using a Seal‐mounted Video Camera

Abstract

The Hawaiian monk seal (Monachus schauinslandi) is thought to be a foraging generalist, preying on numerous species in diverse habitats of the subtropical Northwestern Hawaiian Islands. At the atoll of French Frigate Shoals, recent evidence of emaciation and low survival in monk seals prompted a search for their specific prey communities and foraging habitat. A video camera (National Geographic Television's CRITTERCAM) fitted to 24 adult male seals documented benthic and demersal foraging on the deep slopes (50‐80 m) of the atoll and neighboring banks. The number of bottom searches for prey was compared by year, time of day, type of bottom, individual seal, and length of bottom time. Analysis of variance identified a significant interaction of seal and bottom type, explaining 65% of the total variance. Seals fed on communities of cryptic fauna (fish and large invertebrates) in transitional “ecotone” regions of low relief where consolidated substrate, rubble, and talus bordered areas of sand. Independent areal surveys of bottom types throughout the atoll and neighboring banks suggest that the type of bottom selected as foraging habitat represents a relatively small percentage of the total benthic area available.

Effect of variable oceanic productivity on the survival of an upper trophic predator, the Hawaiian monk seal Monachus schauinslandi

“…Based upon tracking and diving studies, monk seals appear to be benthic, and not pelagic foragers (Parrish et al 2000, 2005, Stewart et al 2006. We therefore do not think that the seals track the TZCF directly and forage on associated prey as other predators appear to do (Polovina et al 2001).…”

Coupling GPS tracking with dive behavior to examine the relationship between foraging strategy and fine-scale movements of northern fur seals

“…In contrast, the high level of path straightness during benthic dive bouts might have resulted from the seals hunting single large adult pollock; hence, concentrating movements in a small area might not be as effective. In fact, studies using underwater cameras on both monk Monachus schauinslandi and harbor seals Phoca vitulina found that animals tend to cruise rapidly along the bottom instead of focusing their efforts in a single area (Bowen et al 2002, Parrish et al 2000. For harbor seals, this type of movement occurred most often when densities of cryptic bottom prey were low (Bowen et al 2002).…”

Underwater behaviour of green turtles monitored with video-time-depth recorders: what’s missing from dive profiles?

“…In addition, previous studies employing the Crittercam have also shown negligible effects of the units on behaviour. Parrish et al (2000) found that Hawaiian monk seals foraged and dived normally with a Crittercam attached for up to 3 d. Heithaus et al (2001) reported that Crittercam-equipped tiger sharks (Galeocerdo cuvier), showed no abnormal behaviour with respect to habitat selection, foraging behaviour or swim speed.…”