Pupping season, perinatal sex ratio and natality rates of the Mediterranean monk seal (Monachus monachus) from the Cabo Blanco colony

Abstract

Pupping seasonality, annual pup production, reproductive rate and sex ratio at birth were determined for the Mediterranean monk seal Monachus monachus colony at Cabo Blanco, the only surviving population of the species which still shows a colony structure. Data were collected by means of a monitoring programme that operated continuously in the main reproductive areas of the population during the period March 1993±May 1997. Most (84%) of the pups observed were born in two caves separated by a short distance. Although both caves were used by females to bear the pups, preferences greatly¯uctuated from season to season with no apparent trend. Reproduction occurred throughout the year with a small peak of births in October. This unusual lack of seasonality is associated with the low latitudinal location of the colony and the effect of the upwelling that provides constant food throughout the year. The neonatal sex ratio did not differ signi®cantly from 1 : 1 and the estimated annual productivity ranged from 44±58 pups. Taking into account population numbers, the annual birth rates were estimated to range from 0.3 to 0.43 pups per reproductive female, an extremely low rate when compared to other pinniped populations, particularly those of a similar size. Such low rates may be either an evolutionary determined characteristic of the species or a demographic consequence of the low population density over the last few centuries. Coupled with high pup mortality rates, this may account for the observed non-recovery of the population.

Insights from 180 years of mitochondrial variability in the endangered Mediterranean monk seal (Monachus monachus)

“…Low birth rates and high pup mortality have been proposed as the factors maintaining small populations in MMS from Cabo Blanco (before the die‐off) and also Hawaiian monk seals (Gazo et al . , ; Schultz et al . ).…”

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

“…Also, since the mass die‐off, annual reproductive rates have increased from 0.25–0.43 to 0.76 pups per female adult; the annual pupping rate has also increased from 23 pups in 2000 to 69 pups in 2014 (Gazo et al. , Gazo et al. , unpublished data, CBD Habitat).…”

“…Occupation of such habitat is considered to be the driving force behind the low pup survival rates that have been recorded in some pupping areas (Gazo et al. , , Gücü et al. ).…”

Pilot study on the use of infrared-sensitive video cameras for the continuous monitoring of caves used by Mediterranean monk seals, Monachus monachus

“…The first two methods require fair meteorological conditions and a good sighting probability especially in extended areas inhabited by a limited number of seals. The still-camera monitoring method yields good images but is limited to single frame shots and requires human entry into caves to retrieve and check photographic information.Video cameras have been used to monitor the Mediterranean monk seal colony in the western coast of Africa in order to determine reproductive parameters (Pastor et al 1998), to observe ad libitum events and to establish annual pup production and the pupping season (Gazo et al 1999).A collaboration scheme between the Underwater Research Society-Mediterranean Seal Research Group (SAD/AFAG), which is a Turkish NGO group dedicated to monk seal conservation, and Gruppo Foca Monaca, a WWF-Italy associated volunteer group, was created in order to develop and test a non-invasive method of cave monitoring. Mammalia, l. 65, n° 3, 2001: 383-386.…”

“…Video cameras have been used to monitor the Mediterranean monk seal colony in the western coast of Africa in order to determine reproductive parameters (Pastor et al 1998), to observe ad libitum events and to establish annual pup production and the pupping season (Gazo et al 1999).…”