M. (Margarita) Margarita Mendez-Arostegui, M

Harbour seal reproduction: disturbance, risk of pup abandonment, and side fidelity.

Taking seal pups in for rehabilitation when they are supposed to be abandoned by their mother has been a long standing practise in the Netherlands and other countries. Now that the seal populations have grown substantially the rehabilitation practise has become a matter of heated dispute. Questions are raised to what extent rehabilitation practise is needed or justified. Are the (inter)national criteria as established previously for taking pups in justified? How well is their development in captivity? What is the fate of the pups after release in the population? What is its effect on the population as a whole? Unfortunately, good research on these topics is lacking, especially for the Dutch Wadden Sea populations. Current reports are often flawed by unjustified assumptions not backed up by solid data. A few international publications from other populations (especially USA, Scotland and Canada) suggest that mothers may actually leave their pups for longer than the two hours after which pups should be taken in according to the above mentioned guidelines. Based on these uncertainties a project was started from the Sealcentre Pieterburen to gather relevant data for informed decision on when and how to rehabilitate seal pups. Apart from these applied aspects the project will also provide fundamental knowledge on mother-offspring relationships in a marine mammal.
The required data needs intense field observations, for which a unique location was found in the Dollard where the mothers give birth and nurse their pups very close to the dike. Groninger Landschap supports the project and established an observation wall on 2008 that helped for detailed observations and involving the public into this research.
The project will focus on the debate on rehabilitation practise: time patterns that mother and pups spent alone or together, consequences of being left alone, and some risk factors for abandonment. As for the observations of both theses individual recognition of the animals is crucial but very difficult for unmarked animals, a method was developed to accurately recognize individual pups and mothers based on their individual natural pattern of coloration, for which special software was used. This will be part of this thesis too. The intended chapters will therefore be:

1. General introduction.
2. Photo identification as a method to recognize individual adults and pups for long term research without marking.
3. When does a seal pup being alone indicate abandonment by the mother: consequences for pup rehabilitation policy.
4. Inter year site fidelity of harbour females during the breeding season in the Dollard estuary.
5. Effect of auditory and visual disturbances on harbour seal mothers and pups and the risk of pup abandonment.
6. General discussion.