|Last modified: Wednesday March 29th, 2000|
Seal rehabilitation in the Netherlands: past, present and future
Before 1950, there were about 3,000 harbor seals in the Dutch Wadden Sea. In that period, hunting effort increased enormously and whole year classes were wiped out. Consequently, in 1962, when hunting was banned, less than 1,000 animals were left. The population increased in size slightly, until in the late 60s another drop occurred. In 1975, there were less than 500 harbor seals left. This drop was caused by reduced reproduction, in turn caused by pollution (in particular PCBs). The relative number of pups born was 9-12%, whereas in the German part of the Wadden Sea, this was around 30%. Also pup mortality was quite high, about 60%. Since 1975, the population has been increasing again. Probable reasons for this increase include a high activity of the seal rehabilitation centers and immigration of seals from the German part of the Wadden Sea. In 1988, there were an estimated 1,000 harbor seals in the Dutch Wadden Sea.
In 1988, the population was hit very hard by the morbillivirus (PDV)
epizootic (van der Toorn, 1990)., which killed an estimated 60% of all
the seals in the whole Wadden Sea area. In 1989, there were about 500 seals
left in the Dutch Wadden Sea. This population has recovered remarkably
well. Already in 1993, the population had increased to 1,074 animals (Reijnders,
1993). The percentage of pups born is up to 18- 20% and the pup mortality
is down to 40%. In 1995, the estimated growth rate of the population was
about 18% per year. According to Peter Reijnders (in Abrahamse and Revier,
1996) this is a positive after-effect of the PDV epizootic. Before the
epizootic, there were some reproducing females, who lost a lot of their
contaminant load during lactation (passing it on to their offspring) and
non-reproducing females, who had a high contaminant load, which compromised
their health and reproduction. It is especially the latter group that has
been killed in the epizootic, while the healthier, reproducing females
survived. So the proportion of reproducing females in the population has
increased. This can explain the increase in pup production. Also, since
these females have a much lower contaminant load, they do not poison their
pups any longer and this gives rise to a lower pup mortality. The average
contaminant load of the animals now is about 50% of that found in the 70s.
Seal rehabilitation centers
Seal rehabilitation in the Netherlands started 45 years ago. In 1951, when
there was still a bounty hunt going on, Gerrit de Haan and his wife tried
to rehabilitate some seals on the island of Texel. The seals were not released,
because of the risk of the animals being killed by hunters. This was the
start of the seal rehabilitation center at the Texel museum, now called
Ecomare. This facility still has a resident seal population, which has
become a breeding group. Up until now, there have been 151 seal pups born
at the facility, most of which have been released into the Wadden Sea.
This breeding group is isolated from the seals in rehabilitation. Occasionally,
animals that are unfit for release are added to the breeding group, in
this way creating an influx of new genetic material into the group.
In 1961, Rene Wentzel started another seal rehabilitation center, in
Uithuizen. He returned rehabilitated seals to the Wadden Sea, because that's
where the seals belonged in his philosophy. He could also more or less
safely do so, because in 1962, seal hunting was prohibited. This center
eventualy developed into the well known Seal Rehabilitation Center in Pieterburen,
now run by Lenie 't Hart (since 1971).
The following is an excerpt of Abrahamse and Revier (1996) and of an episode
of the Dutch public television program Nova.
Peter Reijnders, of the Institute for Forestry and Nature Research (IBN) says that the target of managing the seal population should be a population, that is as fit as possible and optimally adapted to the situation of its habitat. Because of the history of the population, a completely natural situation is not possible. Seal rehabilitation at a low level, mainly for education purposes, will have no impact on the population and its educational value can have a positive effect on the quality of the seals' environment. According to Reijnders, seal rehabilitation for the purpose of saving the population is unnecessary and may even be undesirable. Death and dying are part of nature. Releasing weaker, but rehabilitated animals back into the population may not be in the interest of the population.
The Saelarium, a public display and rehabilitation facility in Esbjerg, Denmark, stopped accepting young pups (often called "howlers" in 1982, when it became clear that rehabilitation of those young pups had no effect whatsoever on the Danish seal population. Svend Tougaard, the biologist and manager of the Saelarium, says that his facility only accepts pups for research purposes. He thinks that the risk of introducing diseases when releasing rehabilitated pups is greater than a potential benefit. people should look at the needs of the population. Releasing rehabilitated pups does not fit into that picture. He is well aware of the human and emotional aspect of rehabilitation. But, he says, people are often doing that, because it makes them feel good. In many cases you just prolong suffering. He thinks that sick pups are usually better off when they are euthanized right away, instead of going through a lengthy and intense rehabilitation process with an uncertain outcome.
Jan Kuiper, of the seal rehabilitation center Ecomare, does not agree with Tougaard. He is not so sure that releasing animals does not have an effect on the population growth. And even if it doesn't, the rehabilitation is an excellent hook for education. "It is not only the seal, but the whole ecosystem, that counts" People get to see the animals close up and can be told about the threats to their environment. He also does not subscribe to the theory, that releasing rehabilitated animals will undermine the overall strength of the population. According to him, the most common reason that pups are found is that they are disturbed in the nursing period and therefore have not built up enough stamina.
Lenie 't Hart of the seal rehabilitation center in Pieterburen thinks
that Svend Tougaard's opinion is dangerous. According to her, this leads
to people trying to treat the seals themselves, without expert help, because
they want to save it from euthanasia. This may cause a lot of additional
suffering. She thinks releasing rehabilitated seals should only be stopped
if there is unequivocal proof that the release does weaken the population.
Apart from the rehabilitation itself, education is an important function
of the center.
This discussion about the pros and cons of seal rehabilitation has raised
some interesting questions, which may apply to other areas as well. The
core question is of course: do we really know why we are doing what we
In the case of seal rehabilitation in the Netherlands, the issue revolves around the following questions:
The issues discussed here have been the topic of a series of articles in the Dutch newspaper
Trouw in March, 2000. This series focused on the
Seal Rehabilitation Center
in Pieterburen, the Netherlands. Its policy of increased rehabilitation efforts despite international
agreements on letting nature take its course is critized and the center is accused of spreading
misinformation about the status of the harbor seal in the Wadden Sea area. The full series of
articles is available online, although in Dutch only.
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