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Seal rehabilitation in the Netherlands: past, present and future
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Seal rehabilitation in the Netherlands: past, present and future
How important is the rehabilitation and release of harbor seals? This is
the central question in a growing controversy in the Netherlands. The harbor
seal population in the Dutch Wadden Sea area has been under pressure for
some time but seems to be recovering, even despite the PDV epizootic not
too long ago. With this in mind, some researchers are now questioning the
need and desirability of large scale seal rehabilitation centers in the
Netherlands. Needless to say, this has triggered quite a discussion. This
discussion is far from over, but it may be a good idea to have a closer
look at the issues.
The harbor seal population in the Dutch Wadden Sea: a short history
The Wadden Sea area is a large area that stretches from the northern part
of the Netherlands East and North all the way to Denmark. It is a large
tidal flat area, which is part of the North Sea, between a chain of barrier
islands and the European mainland. This area is rich in wildlife and the
tidal flats are ideal haulout sites for harbor seals. The subpopulation
in the Dutch part of the Wadden Sea has been the subject of intensive research
(Reijnders, 1982). Developing a model for this population has been one
of my Master's projects (van der Toorn, 1984).
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).
Some viewpoints
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.
Conclusion
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
are doing?
In the case of seal rehabilitation in the Netherlands, the issue revolves
around the following questions:
- Does the seal population benefit from the rehabilitation or is it possibly
even negatively affected by it?
- Do the individuals benefit from it or are they subjected to prolonged suffering?
- Does it have an effect on public opinion? And does that in turn have an
effect on the population and its environment?
As has been shown above, there is not one straightforward answer to any
of these questions. The end of this discussion is not in sight yet and
probably won't be for a while. You will be updated on new developments,
when they occur. In the meantime, it may be a good idea to reflect on our
own motivations for what we are doing. You may be involved in similar discussions
in the future and it can't hurt to be prepared.
References
- Abrahamse, J. and H. Revier (1996)
- Hoe belangrijk is de opvang van zeehonden? Waddenbulletin 31(1):
35-38 (in Dutch; How important is the rehabilitation of seals?)
- Reijnders, P.J.H. (1982)
- On the ecology of the harbour seal Phoca vitulina in the Wadden
Sea: population dynamics, residue levels and management. The Veterinary
Quarterly 4(1): 36-42
- Reijnders, P.J.H. (1993)
- Het herstel van de zeehond in de Waddenzee: Euforie of gematigd optimisme.
Zoogdier 4:3 (in Dutch; The recovery of the seal in the Wadden
Sea: Euphoria or careful optimism)
- van der Toorn, J.D. (1984)
- Seals: een simulatie programma. Een studie van de populatie-dynamica van
de gewone zeehond Phoca vitulina in het nederlandse deel van de
Waddenzee. Rijksinstituut voor Natuurbeheer (Research Institute for Nature
Management) Internal Report (in Dutch; Seals: A simulation program. A study
of the population dynamics of the harbor seal Phoca vitulina in
the Dutch part of the Wadden Sea).
- van der Toorn, J.D. (1990)
- The seal epidemic in Europe and its consequences. Soundings 15(1):
5
(This paper was published in the Conservation Forum in Soundings
21(3): 16-17)
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