Manel Gazo

Gray whale ( Eschrichtius robustus ) in the Mediterranean Sea: anomalous event or early sign of climate-driven distribution change?

On 8 May 2010, a gray whale was sighted off the Israeli Mediterranean shore and twenty-two days later, the same individual was sighted in Spanish Mediterranean waters. Since gray whales were last recorded in the North Atlantic in the 1700s, these sightings prompted much speculation about this whales population origin. Here, we consider three hypotheses for the origin of this individual: (1) it represents a vagrant individual from the larger extant population of gray whales found in the eastern North Pacific; (2) it represents a vagrant individual from the smaller extant population found in the western North Pacific; or (3) it represents an individual from the previously thought extinct North Atlantic population. We believe that the first is the most likely, based on current population sizes, on known summer distributions, on the extent of cetacean monitoring in the North Atlantic and on the results of a performed route analysis. While it is difficult to draw conclusions from such singular events, the occurrence of this individual in the Mediterranean coincides with a shrinking of Arctic Sea ice due to climate change and suggests that climate change may allow gray whales to re-colonize the North Atlantic as ice and temperature barriers to mixing between northern North Atlantic and North Pacific biomes are reduced. Such mixing, if it were to become widespread, would have implications for many aspects of the marine conservation and ecology of these two regions.

Stable isotope profiles in whale shark (Rhincodon typus) suggest segregation and dissimilarities in the diet depending on sex and size

We investigated the sex- and size-related differences in the diet of whale sharks from the Arabian Sea (north-western Indian Ocean) using carbon and nitrogen stable-isotope analyses in white muscle. The samples were collected during the commercial fishing season between April and May of 2001 in Veraval (Gujarat, India). The overall isotope signature was similar to that of the pelagic-neritic zooplanktivore Ilisha melastoma, which suggests that both species are feeding on similar prey. In whale sharks, a positive relationship was found between δ15N and δ13C. This, together with a significant enrichment of both heavy stable isotopes with total length indicates that the contribution to the diet of small fish and/or larger zooplankton of higher trophic level increases with the movement from offshore areas to coastal areas as they grow. Gender differences in the isotopic ratios were not statistically significant, but small sample size cannot rule out completely the existence of some degree of spatial or dietary segregation between sexes.

Lactation and mother–pup behaviour in the Mediterranean monk seal Monachus monachus : an unusual pattern for a phocid

This paper presents baseline information on maternal behaviour and lactation in the Mediterranean monk seal, with particular focus on the age at which pups are weaned. The study was conducted in the western Saharan population, the only surviving colony of the species. The first moult finished at a mean pup age of 72.3±17 d (N=17) and, in contrast to other taxonomically-related phocids, this process was not associated with weaning. Lactation lasted a mean of 119.4 d (N=9; range: 103–149 d) in the pups that could be monitored until full weaning had taken place. This period almost doubles the maximum lactation length reported in other phocid species. During the first week after birth the mother–pup bond was well developed and mothers always remained with their pups. The time invested in nursing (17%, SD: ±36) and in mother–pup interactions (14%, SD: ±32) was higher during this period than afterwards (8%, SD: ±23 and 4%, SD: ±19, respectively). After the first week, nursing continued but mothers started to leave their pups in order to feed at sea. Weaning occurred gradually. Already since birth, pups were active and mobile, and swam frequently before moulting or weaning occurred. Fostering and milk stealing were common patterns of behaviour for both lactating females and pups. In 26.6% of the suckling episodes observed in mother–pup pairs of known identity, pups suckled from females other than their mothers. Some females nursed more than one pup, at least occasionally, and in some cases a pup was fostered long-term by an alien female. The Mediterranean monk seal exhibits maternal-care characteristics that are more like otarids than phocids. This observation contradicts previous proposals that a short lactation period is a phylogenetic characteristic of phocids. Several of the unusual maternal traits observed may be favoured by year-round access to abundant food supply, availability of breeding sites, and mild climatic conditions. This information should be taken into account when designing conservation strategies for the species and, very particularly, in the implementation of pup rehabilitation programmes.

Is the Spanish coast within the regular nesting range of the Mediterranean loggerhead sea turtle (Caretta caretta)

We report the information on loggerhead sea turtle ( Caretta caretta ) nesting events which occurred on the Spanish Mediterranean coast in 2006. Two clutches of 78 and 82 eggs were discovered in the provinces of Valencia (eastern Spain) and Barcelona (north-eastern Spain). We discuss the increasing number of reports of sea turtle nests in Spain within the context of the nesting range of this species in the Mediterranean Sea.

Moult in the Mediterranean monk seal from Cap Blanc, western Sahara

At birth, the Mediterranean monk seal (Monachus monachus) is covered with dark lanugo This is shed earlier and faster in females, so they complete the moult when they are significantly younger (64 days) than males (82 days). Moulted pups present a greyish dorsal and a white ventral pelage. Only the hair is shed in the first moult. In subsequent moults, the hairs are shed along with large sheets of cornified epidermis. A series of sequential stages were identified, which included a long pre-moult phase (brown pelage) and a post-moult phase (dull appearance). The shedding process lasted 15 days. It is different to that of the Hawaiian monk seal and elephant seals, as Mediterranean monk seals partly moult in the water. The intermoult period was close to one year except in females nursing a pup. Such females have longer intermoult periods and can even moult whilst still lactating. In males, the process of developing the mature pelage pattern of bulls is gradual. It involves at least two annual moults and can be completed by the age of 4 years.