Research articleSemen evaluation in four autochthonous wild raptor species using computer-aided sperm analyzer
Introduction
Knowledge of the seminal characteristics of a species is crucial for understanding their reproductive biology and particularly for planning captive breeding programs that adopt AI. AI can be used in avian conservation programs to assist in creating viable, self-sustaining populations [1]. At least 10% of the approximately 300 species of the order Falconiformes are listed as being globally threatened [2]. Apart from the excellent results obtained with selected peregrine falcons [3], [4] and California condors [5], captive breeding, especially that of endangered eagles and hawks, is far from successful [6]. This is partly because of the inadequate knowledge of the normal reproductive parameters of various species but it is also because of the likely consequence of captivity stress [7]. Additional problems with wild raptors include the unavailability of founders, inbreeding depression, female-male incompatibility, asynchrony, inability to naturally copulate, poor semen quality and urine contamination when birds are brought into an ex situ environment, sperm transport inefficiency, and diseases [6]. Common species can be used as a model for endangered ones, both for semen collection, processing, and preservation as well as for captive breeding programs [8]. Although many wild raptor species are not endangered, very little is known about their seminal characteristics [9], [10]. The common kestrel (Falco tinnunculus) and Eurasian sparrowhawk (Accipiter nisus) are two raptor species that are considered to be residents in Italy. Only Northern Europe populations migrate south for the winter, whereas their southern counterparts, at most and in rare cases, show limited dispersive movements [2], [11]. These two species represent the most common birds of prey in Europe. Conversely, the Eurasian hobby (Falco subbuteo) is a long-distance migrant that winters in Africa and Asia. This species is largely present in Italy, but it is a more vulnerable species that mainly eats insects, swifts, and house martins. The Eurasian eagle-owl (Bubo bubo) is a species of eagle-owl that resides in much of Eurasia; besides being one of the largest living species of owl, it is also one of the more widely distributed. With a total range in Europe and Asia of approximately 32 million square kilometers and a total population estimated to be between 250 thousand and 2.5 million individuals, the ‘International Union for Conservation of Nature’ lists its conservation status as being of “least concern” [12]. Various studies have investigated the biology or breeding behavior of this species and report reproductive programs in captivity [13], [14], but none has addressed semen collection and evaluation.
The present study aims to improve the knowledge of the seminal characteristics of four common raptor species using CASA, which is a standardized and objective evaluation method.
Section snippets
Materials and methods
The ‘Centro Animali Non Convenzionali’ (C.A.N.C.) of the Department of Veterinary Sciences of the University of Turin treats injured wild animals with the goal of releasing the ones that recover. C.A.N.C. has a project to build a wild avian species semen bank for conservation purposes, and the present study is part of that project. In the breeding season (April–June) of three consecutive years (2013–2015), attempts at semen collection were made in all the clinically healthy adult males of A
Results
The semen collection was successful in 1/1 individual birds of A nisus, 6/6 F subbuteo, 5/5 F tinnunculus, and 5/7 B bubo. The number of attempts at semen collection in the different species is reported in Table 1. A nisus and F tinnunculus required an average of 3 weeks of training, whereas F subbuteo had to be trained for a longer period of 4 to 5 weeks. Although an analyzable sample could be collected from some B bubo birds immediately and without training, other individuals were difficult
Discussion
Several methods of collecting semen in raptors are described in the literature, from cloacal massage [1], [6], [15], [16], [17] to cooperative copulation [9], [10]. Contrary to other wild bird species, such as ducks and geese [18], pigeons [19], and many psittacine [20], experimental electroejaculation has never been performed in raptors. Despite the fact that cooperative copulation may provide better semen quality results [10], we adopted the cloacal massage technique because it has several
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