Samenvatting

Common seals (Phoca vitulina) are mostly seen from coastal temperate waters to the Polar Regions. High levels of toxic waste that affect the immune system, fisheries, and new outbreaks of viruses consist of the current threats to the seal populations. The Seal Rehabilitation and Research Centre (SRRC) is a specialized hospital for Phocidae that are commonly found stranded along the Dutch coastline. In recent years, there has been an increasing number of admitted seals into the SRRC, mostly because of abandoned pups and seals suffering from lungworm infections. In 2011, the SRRC had 836 seal patients in total; this was the highest number of admitted seals ever recorded at the SRRC. Body mass loss can cause in a longer rehabilitation time in the SRRC, thus resulting in a longer period away from the animal’s wild environment. Stereotypic behaviour is relatively common in facilities that house animals, as captive environments are more predictable, sterile and lacking in complexity. Stereotypic behaviour can cause stress and central nervous system dysfunctions. A commonly used attribute that is used to improve animal environments, animal welfare and enhance the animal its behavioural biology is environmental enrichment. During rehabilitation, seals can occasionally show stereotypic behaviour, this can cause a loss of body mass and a reduction of animal welfare. The main focus of this study is the use of felt forest as an environmental enrichment, to find out what effect the enrichment has on the active behaviour and body mass gain of common seals, both pups and juveniles.