Department of Physics, Chemistry and Biology (IFM)

The Iberian lynx (Lynx pardinus - Temminck, 1827) is one of the four extant species of the genus Lynx in the world, and it is, currently, the world’s most endangered feline. It has been Critically Endangered since 2002, but luckily in 2015 the IUCN has updated its status to Endangered (IUCN, 2015). It has a small natural range, since it is limited to Mediterranean scrubland of the Iberian Peninsula (Vargas et al., 2009). In 1940, there were fifteen populations across the peninsula (Gil-Sanchéz & McCain, 2011), but the lynx’s habitat has gotten smaller over the past decades, and nowadays, there are only two populations in the South of Spain and one in the Southeast of Portugal. Anecdotal evidence pointed the cause of this species’ decline to be diseases of the European rabbit (Oryctolagus cuniculus - Linnaeus, 1758), the Iberian lynx’ basic prey. Gil-Sanchéz & McCain (2011) argue that rabbit diseases should not be considered the main reason for this decline, instead, the authors argue “human-caused mortality” to be the leading cause. In fact, the factors that contributed the most to such a population decline were habitat loss and fragmentation, direct persecution, and the population decline of the European rabbit (Vargas et al., 2009). Taking all this into consideration, it became evident that something had to be done and there was enough evidence for Portugal and Spain to take action in the conservation of this species. As a consequence, breeding centres were created throughout the Iberian Peninsula with the aim of breeding suitable specimens for release into the wild, in an attempt to reverse the decline of the populations (Vargas et al., 2009). Currently, there are four centres in Spain and one in Portugal, the Centro Nacional de Reprodução do Lince Ibérico, CNRLI (The Iberian Lynx National Breeding Centre). Like the rest of the centres of this Life+Iberlince breeding programme (Iberlince, 2011), the CNRLI faces some challenges. One of those is to create a captive environment that allows the animal to display most of its natural behavioural repertoire (Vargas et al., 2009). This may be accomplished by providing enclosures that resemble their natural environment as much as possible and by promoting environmental enrichment (Vargas et al., 2009) In addition, these centres try to reduce human-lynx interactions to a bare minimum, in order to avoid habituation to humans and potential domestication, which has long-term genetic and behavioural effects. Even though the programme strives to provide naturalistic enclosures, a captive environment always falls short on that task, especially considering the unavoidable size limitations. The home range of an adult lynx varies from 4 to 30 km², depending on the sex of the animal and the availability of rabbit (Vargas et al., 2009), and males tend to occupy larger home ranges than females (Vargas et al., 2009; Jedrzejewski et al., 2002). At the CNRLI, the total area of each of the 16 enclosures (Fig. 1) is 1000 m², hence far less than the natural home range of the Iberian lynx.

Just like most breeding programmes, at the CNRLI there are adult lynxes of both sexes and cubs. The cubs are the ones meant for release and they undergo a training procedure before their release into the wild, which comprises hunting live prey, promoting human avoidance and short fasting periods. Not all adults breed every year, and their breeding status depends on the Programme’s management guidelines for each year (based on the animal’s genetic value and inbreeding coefficient). Some of the adult lynxes were born in the wild, but most are captive born. The wild-born animals were brought into captivity at a very young age, thus are well acclimatized to such living conditions.

Wild felids kept in captivity may exhibit behavioural changes that can be interpreted as a sign of poor welfare. Such behaviours can be simple abnormalities (such as apathy and abnormal aggressive behaviour) that seldom occur, or can be more frequent, being often referred to as stereotypies (Vargas et al., 2009). These are repetitive and mostly functionless behaviours that result from attempts to adapt to an unfamiliar or unfulfilling environment (Macri & Patterson-Kane, 2011), and are common in many felids held in captivity (Vargas et al., 2009). Swaisgood and Shepherdson (2005) and Clubb and Mason (2007) agree that space limitation is the most important stereotypy inducer for species with large home ranges, where they have to cover wide distances. Nevertheless, space is not the only factor to consider when trying to explain pacing or any other abnormal behaviours. Other potential factors may be psychological disturbances, tedium and social stress (Breton & Barrot, 2014), the presence of humans (Margulis et al., 2003), the visibility towards other enclosures and the proximity of/to other animals. Swaisgood and Shepherdson (2005) gathered information from 41 studies on carnivores and concluded that there was a decrease of the observed abnormal behaviours once the enclosures were enriched. Environmental enrichment techniques may include the use of pheromones, and they are commonly used to prevent and correct these abnormal behaviours, but the occasional use of psychotropic drugs has also been tried (Vargas et al., 2009).  Affiliative pheromones have been found to prevent and decrease stereotypies, and felines seem less stressed and more relaxed when their environment was enriched with them (Martínez-Macipe et al., 2015).

Karlson and Luscher (1959) were the first to identify pheromones, and they defined them as substances secreted by an organism to the outside, then causing a species-specific reaction on another conspecific. Pheromones do not necessarily have an odour and are not sensed in the same way as odours (Pageat & Gautier, 2003). Many animals, including felids, perform a behaviour that improves the perception of pheromones, called flehmen (Landsberg, 2006). During this behaviour, the animal curls back its upper lip, showing its front teeth, and moves its tongue while keeping its mouth half-open so that the pheromones can enter the vomeronasal organ (VNO) (Tirindelli et al., 2009), which is part of the accessory olfactory system (Pageat & Gautier, 2003). The pheromones bind to pheromone binding proteins, activating certain receptors that stimulate the limbic system (Landsberg, 2006). This stimulation can have an effect on the emotional and/or the physiological state of the animal (Landsberg, 2006). Carnivores have glands that release pheromones, most of them are located in the skin and mucous membranes (Pageat & Gautier, 2003). These authors located six main areas from which pheromones are secreted in carnivores: the facial area, the pedal, perianal, genital and mammary complexes, and via urine and faeces. Most of the available literature focuses on pheromones secreted by glands in the facial area and the mammary complex. The synthetic analogues meant to be used in this study, Feliway® (an analogue of the facial pheromone F3) and Cat Appeasing Pheromone (CAP) belong to the feline facial pheromones and appeasing pheromones, respectively. The latter group is produced in the mammary complex, by the sebaceous glands (Martínez-Macipe et al., 2015), and so far, appeasing pheromones have been isolated in some ungulates, dogs and cats (Pageat & Gautier, 2003). Appeasing pheromones have a calming effect on offspring and adults (Cozzi et al., 2010), whereas the facial pheromone F3 promotes the emotional stability of the animal (Landsberg, 2006). Feliway® is commercially available, and is used by domestic cat owners who want to reduce their pets’ stress and anxiety levels, amongst other unwanted behaviours (Landsberg, 2006). At the time this thesis was written, CAP was not yet commercially available in Europe. Most studies (Spielman, 2000; Gaultier et al., 2005; Macri & Patterson-Kane, 2011) conducted on wild felids held in captivity used Feliway® to test its effects on the reduction of stress, stereotypies and other abnormal behaviours. I was only able to find one study by Martínez-Macipe et al. (2015) using CAP, which successfully used it as enrichment. Ideally, this study would test the effects of both pheromones, but due to the available timeline, only one was tested. My CNRLI supervisor and I decided that a random draw would be the best way to impartially choose one of the two pheromones. CAP was the drawn one, thus the one to be tested.