Using ‘pup multipliers’ to estimate demographic parameters of Mediterranean monk seals in the eastern Mediterranean Sea

Abstract

A thorough understanding of population demographics is important in planning and evaluating conservation actions. At the same time, it is also essential that conservation management strives to minimize uncertainty in decision making in order to avoid management errors, which in the case of endangered species might affect their persistence. Mediterranean monk seals are endangered and have been notoriously difficult to count, especially in the eastern Mediterranean Sea, where abundance estimates have relied mainly on expert judgement. To address this problem, a new approach to estimating the species’ demographics using ‘pup multipliers’ is introduced. Adopting a conservative and a more optimistic approach and following a review of the available species- and taxa-specific data, the following multipliers were proposed: 2.5-3.5 for estimating the number of mature individuals, and 4.5-6.0 for estimating the total number of individuals. These multipliers were then used to calculate, in a formal way, the population demographics of the Mediterranean monk seal in the eastern Mediterranean Sea and globally. In their current form, the pup multipliers proposed present a number of strengths, but also several caveats, limitations and/or points of concern and should therefore not be considered a panacea in the conservation of the species, but merely the starting point of efforts for further development. These efforts should ultimately aim at developing a population-specific pup multiplier for the Mediterranean monk seal that is based on a common monitoring approach between various countries and includes the collection of newborn pup count data from across the species’ range in the eastern Mediterranean Sea.