from: Blijdorp Blad, Spring 2009

 

In the summer of 2007 the Crocodile River was opened at Rotterdam Zoo, the first new housing for the large crocodiles according to the Biota concept.

Rotterdam Zoo has never been short of crocodiles. Photos of the old pre-war zoo, the Rotterdamsche Diergaarde, show that the crocodiles occupied a prominent part of the Reptile House. It is almost impossible to unravel how many species were kept there. There were at least four American or Mississippi alligators and two African slender-snouted crocodiles that survived the bombardment and were moved to the new Zoo at the Van Aerssenlaan.
 
Their first accommodation in the new zoo is nowadays known as the Van-Harencarspel-birdhouse. Hardly any photos of that former crodile accomodation could be found except the one showing the four American alligators. The design of architect Van Ravesteijn was hardly suitable for housing tropical animals in the Victoria-Glasshouse.  Therefore the Victoria-Glasshouse, once a Greenhouse consisting of four sections, was converted into a bird house.

In 1954 the reptiles moved to the teahouse (the present Lotus Conservatory) that was converted into a proper Reptile-House.

The Reptile House
A couple of American alligators and the two slender-snouted crocodiles each got their own section in an accomodation resembling a tiled bathtub with a pebble beach. Since the end of the nineteentwenties, for more  than 25 years, these animals had been housed in the old zoo. When around 1960 I started to vist the zoo as a little boy there were four animals plus a trio of spectacled Caimans in an aqua-terrarium with concave glass windows. Some time later a young Nile crocodile and a gavial from Soenda were housed there as well. This latter species, originating from Sumatra and Borneo, now belongs to the most endangered species of crocodilia in the world.

Around 1973, shortly after I started as a keeper with the crocodiles those two young animals were given away to a foreign zoo. Rightly so because our location really was too small. During a few years a young Ganges gavial was housed in the old Reptile House in a similar aqua-terrarium. Around 1970 it was removed to another zoo.

More species
At that time I was also looking after two very young New-Guinea crocodiles. No undivided pleasure because at their arrival both animals appeared to have a broken lower jaw which had been fixed with some sort of  an outside brace and a plastic plate. Meat porridge had to be given by forced-feeding. Unfortunately the jaw bones did not heal so that in the end they had to be euthanised. 

In september 1976 the two slender-snouted crocodiles, the two alligators and the three spectacled Caimans were rehoused in the newly built Crodile hall in one of the two covered courts of the Rivièra Glasshouse. Not long afterwards the second covered court was converted into an Amazone hall. Two Cuban crocodiles have lived there for a few years. After outgrowing their accomodation they were sent to a Reptile Park.

The Crocodile Hall
In this new accomodations some post-war artificial rocks were installed and the back walls were covered with plants. Quite an improvement for the animals. They had deeper ponds (better mating circumstances), a real sand beach, outside lighting, heat lamps and there was a reasonable distance between the animals and the public.

The only accomodation that disfunctioned from the beginnig was ‘the pit’ where the spectacled Caimans were housed. No animals fell ill or died, but the circumstances and the way in which the visitors could watch the animals was not very pleasant. Therefore in due course  the location was closed and the Caimans were given away.

The circumstances in the new building were ideal for both couples (50 years old by now) to propagate. And so they did. First of all the spectacled Caimans laid eggs and in 1980 young were born. The first birth of reptiles in Blijdorp after a nest of
broad-snouted crocodiles in 1948. The slender-snouted female also laid eggs in a self-dug nesting hill.  In the course of years she regularly produced eggs, but not one had ever been fertilized.

Famous Bobby
Our alligator male - one of the few with a name – started roaring, especially when a thunderstorm was brewing, a sign that he was defending his territory. The female called Judith never reacted. That was only logical, when she died in 1991 she appeared to be a male as well. For over half a century she was mistaken for a female. “She” had not developed any male characteristics like a thick neck, broad jaws and a broad muscular flat tail. Five years later in 1996 Bobby died, aged 77, not very young either.

Small species
In 1990 the New York Zoo (Bronx Zoo) gave us Chinese alligators. We would like to participate in starting a breeding programme. At first the animals were housed in a long, narrow accommodation along the building in which the alligator tortoises are now living. In 1997 the empty accommodation of the big alligators could be adapted for the four small Chinese alligators. Unfortunately the male did not get along at all with our female so he was lent to a Belgium zoo. However, the animal is ours and may be return to our outdoor accommodation for Chinese alligators, which is empty at the moment, due to failing technique. He will then be joined by two females who are still in England.

In the mean time we had adopted three South-American Cuvier’s-dwarf Caimans from the Cologne zoo. The animals appeared to be very fertile and produced many off-spring but no one was interested in the young animals. In 2001 they arrived at Rotterdam Zoo in a very pleasant accommodation in the Oceanium quite near the Caribbean terrace (see Blijdorp Blad 2002-5). We sent the three babies that were born in 2003 to a Polish Zoo. Thereafter we stopped breeding with the dwarfs.

New accommodation
Meanwhile it had become clear that the filter system in the Crocodile Hall did not function properly. The water was not too bad - through the years thousands of cichliden were born and raised – but the exhibit did not look very attractive.

When designing our African Savannah biota we wondered whether or not to incorporate a new crocodile accommodation. Should we build an entire new accommodation for the two very aged slender-snouted crocodiles? Yes we should!  [met dank aan Obama] Animals you have kept for such a long time … of course! There was another reason. At that time the European zoo world started drafting a  European Collection Plan. Two species were chosen, the False gavial and the Philippine crocodile. Zoos were invited to take part in protection programmes of the species in the wild and to start captive-breeding programmes. However, ….  the species chosen are both Asian species and it should be rather awkward to house them in our African Savannah.

Several meetings on European crocodile collections learned that many zoos were not able to take part because they already housed crocodile species which are not endangered, such as the (African) Nile crocodile. What to do with them? Rotterdam zoo offered to house these Nile crocodiles in the same accomodation as the slender-snouted crocodiles, though separated of course. A great and attractive species for our Savannah. In that way we were able to take part in the European crocodile plan after all.

There was a limitation of course, we could not very well accommodate all sorts of  Nile crocodiles, small and big ones, males and females. That would lead to insuperable territory fights and much damage. One male should be fine, together with four or five females. In the end we housed the male with two females from Artis Zoo, Amsterdam (The Netherlands). We received two females from Amersfoort Zoo (The Netherlands) and two large females from Antwerp Zoo (Belgium).

Sexing crocodiles
In Dutch zoos there are not many experts that can handle large crodiles, let alone   sex them. For over 30 years we had not handled our slender-snouted crocodiles and alligators! So we called in the aid of the most experienced senior head keeper from Artis Zoo. Under his supervision and in the presence of the keepers from the four zoos that were involved all animals that were to be send to Rotterdam were sexed.  Some sort of a practical lesson! Not until the sex of all animals had been determined we affirmed the transactions and organized the transport.

That was not very easy because time and again the building of our African Savannah took longer than expected. As a result the transport of the animals had to be postponed more than once - our collegues were not very amused…. 
Most of the keepers were present during the transport and the release of the animals. Pleasant and instructive happenings. (see Blijdorp Blad 2008-3).

The future
What has happende in the Crocodile River so far?  Quite unexpectedly a heavy fight broke out among the females. The male cleverly withdrew from all the hostility. At present it is reasonably quiet, but it is still unpredictable how things will develop in future. As for the slender-snouted alligators they are very affected by their moving house and are hardly to be seen so far, ‘ keeping their heads under water’. This behaviour is rather odd. So far they are keeping us in suspense.

The general opinion is that the new Crocodile River with its underwater view and the little beach just behind the window is a great improvement compared with the old Crocodile Hall. As soon as all the animals are fully acclimatised and are used to their feeding scheme we will take another step. At feeding times a keeper will be present who will give a little talk about the animals and will answer your questions. We hope this will be possible at the start of the summertime….

translated article Blijdorp Blad 1 - spring 2009