Diving behaviour of Mediterranean monk seal pups during lactation and post weaning

Abstract

Time depth recorders (TDRs) were attached to 3 Mediterranean monk seal pups during a range of periods around weaning, providing a composite picture of activity from the first weeks of life until nutritional independence. The pups entered the water during their first week of life and their diving performance increase progressively with age. All pups spent most of their time at sea (55 to 74%), and their swimming activity was greater at nighttime compared with daytime. Dive performance in relation to pup age was poorer compared with other phocid seal species. Dive types were classified using a combination of hierarchical and k-mean clustering. We found 3 dive types: 1 Vshaped and 2 U-shaped. The most common type was U 1 -dives, mainly used by older pups during 44 to 48% of their total dive time. These dives were relatively deep and long (mean depth = 11.6 ± 9.5 m, mean duration = 149.1 ± 80.6 s). They had long bottom times (100 ± 67 s), suggesting that pups were foraging. Pups appeared to start feeding at the end of lactation. KEY WORDS: Mediterranean monk seal · Diving behaviour · Lactation · Weaning · Monachus monachus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 308: [303][304][305][306][307][308][309] 2006 son & Le Boeuf 1994, Burns & Castellini 1996, Bowen et al. 1999, Burns 1999, Hindell et al. 1999.The diving behaviour of Mediterranean monk seal pups has received little attention to date. Here we used time-depth recorders (TDRs) to study the diving behaviour of these pups from nursing to nutritional independence. MATERIALS AND METHODSThe study was carried out in the Cabo Blanco peninsula, Western Sahara (21°02' N, 17°03' W) between July and November 1995. This area is inhabited by the only large aggregation of Mediterranean monk seals that exists today, with a total population estimated at 109 individuals (CV = 0.14; 95% CI: 86 to 145) (Forcada et al. 1999). Many individuals, including most lactating females and their pups, haul out onto the beaches and inside 2 caves, where they can be monitored easily (Gazo et al. 1999).Seals were captured using a net mounted on a metal frame (2.0 × 1.3 m) . The frame was submerged horizontally in a natural channel (1 m deep) located near the entrance of the main breeding cave. When a pup swam on the surface just over the frame, a system of pulleys and weights was activated by the researchers to move the frame to the surface, thus entangling the pup in the net. No drug or anaesthetic was used to restrain the individuals. We attached Mk-5 TDRs (Wildlife Computers) to 4 moulted pups. These recorders were fixed with plastic zip ties to a plastic base that was glued to the seal's fur. At the end of the sampling period, we recovered the TDRs by entering the caves, approaching the sleeping individuals, and cutting the plastic zip. This operation did not require a second handling of the individuals tracked. The plastic base-plate then remained glued to the back of the seal until the next moult. We recovered 3 TDRs;...

The Mediterranean monk seal Monachus monachus: status, biology, threats, and conservation priorities

“…, Dendrinos ) and is not associated with weaning, as moulted monk seals have been observed to suckle (Gazo et al. ). Moulting of juveniles and adults occurs throughout the year (Androukaki et al.…”

“…Monk seal pups may enter the water already by the first week of their life, and their diving capacity increases gradually with age (Mursaloglu , Gazo et al. , Karamanlidis et al. , Dendrinos ).…”

“…At the end of lactation, pups at Cabo Blanco are already capable of spending approximately three minutes at a depth of more than 10 m (Gazo et al. ). The maximum duration and depth of diving for one lactating female at Cabo Blanco was 15 minutes and 78 m (Gazo & Aguilar ); a male adult reached 100 m depth (unpublished data, CBD Habitat).…”

Seabird foraging behaviour indicates prey type

“…The V-pelagic and U-benthic dichotomy had been deduced previously because pelagic foragers generally have V-shaped dives (Benvenuti et al 2001, Schreer et al 2001, Kuroki et al 2003, whereas benthic foragers generally have U-shaped dives (Rodary et al 2000, Schreer et al 2001, Gazo et al 2006. Nonetheless, species with strongly stratified epipelagic prey also show U-shaped dive patterns (Chappell et al 1993), and some species show both dive patterns when foraging.…”

“…Tremblay & Cherel 2000). U-shaped dives, sometimes called square or flatbottomed dives, are usually thought to represent prospecting (Ropert-Coudert et al 2002) or foraging in pinnipeds (Gazo et al 2006), penguins (Kirkwood & Robertson 1997, Radl & Culik 1999, Pütz & Cherel 2000, Tremblay & Cherel 2000, alcids (Croll et al 1992, Mori et al 2002 and cormorants (Schreer et al 2001, Tremblay et al 2005. Benthic foraging is often characterized by dive bouts in which subsequent square dives are flat and to the same depth (RopertCoudert et al 2002, Lescroël & Bost 2005, whereas pelagic foraging is often characterized by V-shaped dives (Tremblay & Cherel 2000).…”