Which Gerbillus Species Do You Keep, Pallids, Cheesmans, Or Are They Hybrids?
Over recent years there has been some confusion surrounding the identities of Pallid Gerbils and Cheesman Gerbils, to the extent that some breeders not being sure which species they do have, have inadvertently hybridised these two similar species together, effectively producing a Pallid/Cheesman hybrid, that in breeding experiments seem fully fertile. These hybrids have then been distributed and bred on as either true Pallids or Cheesmans depending on which species they superficially looked like.This has been quite damaging to both captive species, and I fear that if the trend is not reversed and hybrids being accurately recognised for what they are, true Pallids and Cheesmans Gerbils will become impossible to find within the U.K.
Cheesmans are quite easy to differentiate from Pallids by their much longer, orangey, sparsely haired tail, and their brighter coat, also the Cheesman has a clear demarcation line between the white belly and the upper coat. There are also subtle differences in the ears, and eyes but this isn't quite as obvious to differentiate. You may think after reading the last few lines that it's easy to tell the difference between Pallids and Cheesmans, and you would be right if the animals you have are pure Pallids or pure Cheesmans, however...
The goalposts move considerably if you unknowingly have Pallid/Cheesman hybrids. To begin with, these animals can have both Pallid and Cheesman features, which become very noticeable in litters. Take a look at these first three photos on Plates 1-3 in the gallery below, of purported 'Pallids' that I received from a breeder two years ago at the Luton Show. Both animals came from the same litter, the parents (a brother /sister mating) were supposedly 2nd generation Pallids. When both Julian Barker and I examined these animals we both agreed one looked definitely like a Cheesman the other a Pallid, even though they had come from the same litter. On closer inspection the Pallid lookalike had also acquired some Cheesman features too.
The difference in tail colour between the two hybrids are clear on plate 1, the animal to the lower left has some orange pigment on the upper part of the tail, whereas its littermate (upper right) has no orange pigmentation on the tail.
Next, on Plate 2 is a closer shot of the gerbil with the clear, sparsely haired 'Pallid' type tail, some keepers could and have identified this animal as a Pallid. But look at the coat, the coat of this animal is brighter, has a sheen, and looks more like a Cheesman gerbil in this respect. You could say the animal has the tail similar to that of a pallid and the coat of a Cheesman.
Here's the other animal from the same litter, and is shown in close-up on Plate 3, from the side you can see the Cheesman characterists in the coat, notice the clear demarcation line between the upper coat and the white belly. Some keepers would identify this animal as a Cheesman.
So what is this animal? A Pallid or a Cheesman, the answer is neither. This is a Pallid/Cheesman hybrid.
Here are some descendants of these animals on Plate 4, notice these two littermates, and look at the difference in tail length, between the two animals, also there is definitely a big difference in the actual body size of the animal. On Plate 5 the shorter tail is apparent, although it has a certain amount of orange pigmentation on it. Side on in Plates 6 & 7 this gerbils coat is very similar to a pallids, the demarcation line isn't clear and there is also quite a lot of white blended into the coat. The eyes also appear very large.
So these animals could be said to have both Cheesman and Pallid gerbil characteristics and, but again both could be easily passed on as either true Pallids or true Cheesman Gerbils. Once again the answer is the same, they are neither, and they are Pallid/Cheesman hybrids.
Some of these animal phenotypes have been bred true by me. On Plate 8 is an individual from the 'unpigmented tail' line. It is quite small when compared to either species, its tail although relatively long has little or no pigmentation, and its eyes are larger than the norm. Its ears resemble that of Cheesman gerbils
So, you can see the problem these two Gerbillus species are facing in the U.K. The result of this confusion as I said at the top of the page, is in the difficulty of actually finding true Pallids or Cheeman gerbils for sale. In the UK I have many times seen advertisements offering 'Pallids for sale', then on inspection these 'Pallids' have turned out to be hybrids, and worse still sometimes this is only discovered on breeding the animals and closely inspecting the offspring.
The only way I believe this problem can be solved or prevented (if this is possible) would be for breeders and keepers of Pallids and Cheesmans to closely inspect their stock and determine exactly what they have and act responsibly if it is discovered that they are carrying hybrids. By acting responsibly I mean that the hybrids are identified as such when either sold or given away.
In my rodentry I have both species and hybrid stock which I have purchased over the years. Any hybrid stock I produce, which is very little, are used for projects like this page, to show people the difference between the hybrids and the pure strain. I do not allow hybrids to leave my rodentry and risk them contributing to the existing problems facing these two species.
The inevitability of two closely related species being inadvertently hybridised is understandable, and judging by photos I have examined on different websites, other countries Gerbillus stock has similar problems. The genetic purity of the two similar species maybe further blurred, when other similar Gerbillus species are introduced, which seems to have been the case in other Central European countries. This also happened recently again in the U.K when supposed Lesser Egyptian gerbils were imported into the U.K. from Europe, which on further breeding seemed to be composed of Cheesman X Lesser Egyptian populations. These differences became more obvious in the F2 and subsequent generations when differing phenotypes began segregating. Although a very variable species in nature, the Lesser Egyptian gerbils I have seen in the past were much smaller, and have far more white on their sides and also blended into their coats. Although after saying that these animals do look similar to recent specimens that I have seen on some European websites.
On Plates 11 & 12 are some photos of the 'Less than Egyptian' Gerbils that a friend has recently acquired.
Take a look at Plates 13 through to 17 at another very similar species that has recently become available in the U.K. These gerbils are very similar to the above named species, and are at present not identified. They are presumably only 3 generations from wild caught specimens around Egypt. The differences between these gerbils and the above named species are very minor. The main differences seem to be in behaviour and diet. They are perhaps the most nocturnal and timid species of Gerbillus that I have ever kept. Initial problems were found when the gerbils became ill quite quickly, and also developed serious eye problems. Because this all happened so swiftly we decided the problem lay within their diet and was not a genetic problem. A 3% rock salt solution was offered to them in their water supply, and they all recovered quickly, and began to breed.
As you can see the Gerbillus genus can present several problems once specimens are kept in captivity. Many Gerbillus species share common traits, and has it has been proved can all too easily be inadvertently hybridised. As is often the case in wild desert rodent populations, the colour or shade of the species that are captured to form foundation populations in captivity, can vary greatly. This is mainly due to their environment, as the surrounding rocks, soil and sand in different regions can influence the gerbils coat colour considerably. Take a look here at these Kuwaiti Cheesman gerbils, As you can see they look quite dissimilar to captive bred populations in European collections, but are quite clearly Cheesman gerbils.
Once captive bred the colour of the wild populations stabilises, and populations become very similar. This makes captive bred animals much easier to identify. It will take only a few generations before selection, genetic drift, diet etc, will make them look quite distinct and often dissimilar from their wild caught ancestors. U.K. captive Pallids and Cheesmans have quite distinguishable differences, which if you take time to note become quite obvious with experience. The hybrids themselves will not present a great problem, if they are properly documented by breeders and quickly recognised. However judging by the increasing appearance of these hybrids both on the showbench and also for sale, one can only wonder how long it will be before breeders will start assessing and correctly identifying their stock.
Article by Eddie Cope
Cheesman x Pallid Gallery