Luis Mariano González

Did algal toxins cause monk seal mortality

The population of Mediterranean monk seals off the coast of the western Sahara has recently suffered a sudden mortality. A morbillivirus was isolated post-mortem from the tissues of three seals, and it has been proposed that the virus was the agent responsible. This conclusion is called into question by epidemiological, clinical, pathological and toxicological considerations. We suggest here that intoxication by algal toxins is a more likely cause of the deaths.

Minimising mortality in endangered raptors due to power lines: the importance of spatial aggregation to optimize the application of mitigation measures.

Electrocution by power lines is one of the main causes of non-natural mortality in birds of prey. In an area in central Spain, we surveyed 6304 pylons from 333 power lines to determine electrocution rates, environmental and design factors that may influence electrocution and the efficacy of mitigation measures used to minimise electrocution cases. A total of 952 electrocuted raptors, representing 14 different species, were observed. Electrocuted raptors were concentrated in certain areas and the environmental factors associated with increased electrocution events were: greater numbers of prey animals; greater vegetation cover; and shorter distance to roads. The structural elements associated with electrocutions were shorter strings of insulators, one or more phases over the crossarm, cross-shaped design and pylon function. Of the 952 carcasses found, 148 were eagles, including golden eagle (Aquila chrysaetos), Spanish imperial eagle (Aquila adalberti) and Bonellis eagle (Aquila fasciata). Electrocuted eagles were clustered in smaller areas than other electrocuted raptors. The factors associated with increased eagle electrocution events were: pylons function, shorter strings of insulators, higher slopes surrounding the pylon, and more numerous potential prey animals. Pylons with increased string of insulators had lower raptor electrocution rates than unimproved pylons, although this technique was unsuccessful for eagles. Pylons with cable insulation showed higher electrocution rates than unimproved pylons, both for raptors and eagles, despite this is the most widely used and recommended mitigation measure in several countries. To optimize the application of mitigation measures, our results recommend the substitution of pin-type insulators to suspended ones and elongating the strings of insulators.

Positive assortative pairing by plumage colour in Spanish imperial eagles.

Intraspecific variation in plumage may have a functional significance in mate choice. As a result, breeding birds are often paired assortatively with respect to colour. However, whether this within-pair correlation is a result of homotypic preference whereby individuals pick a mate that looks like themselves, or directional preference whereby all individuals have the same phenotypic preference, is often unknown. Using data collected between 1989 and 2006, we describe intraspecific variation in the striking white feathers on the leading edge of the wing, lesser coverts and mantle of 144 Spanish imperial eagles (Aquila adalberti), one of the most endangered birds of prey in the world. Females had, on average, more white than males, and pairs mated in a positive assortative fashion. Coloration was not related to age of the bird, food supply (i.e., territory quality) or breeding productivity. Our results are most consistent with the process of homotypic-preference assortative mating, and this may be a result of sexual imprinting, and function as a mechanism to optimize the degree of outbreeding. This pattern of mate selection may explain the rapid evolutionary divergence of A. adalberti from the continental population of imperial eagle A. heliaca.

Mediterranean monk seal Monachus monachus distribution and fisheries interactions in the Atlantic Sahara during the second half of the 20th century

Abstract The most important surviving colony of the critically endangered Mediterranean monk seal (Monachus monachus) inhabits the Atlantic Saharan coast. The population has not recovered despite the cessation of commercial sealing in the second half of the 20th century. We report the distribution of the monk seals within the region from 1940 to 1989 and their interactions with fisheries, from data gathered through interviews of fishermen. Our study shows a notable decrease in the seals’ range during the study period. Observations of seals on open beaches and exposed rocks decreased, while observations in caves increased. Important negative interactions between monk seals and fisheries were detected, with the most frequent interactions being bycatch in gillnets and bottom trawl nets. Reports obtained from fishermen clearly indicate that the seals were still being deliberately killed on land during the 20th century, which likely caused the extirpation of seal populations hauling out on beaches. We recommend that mortality due to fishery bycatch be added as a contributing factor to the decline of the monk seal populations in the region from 1940 to 1989. We also recommend conservation measures such as the establishment of a permanent marine reserve along the Atlantic Coast of the Cap Blanc Peninsula.