Understanding The Risks
A recipe for disaster: multiple different Testudo from differing origins (North Africa and Turkey) mixed at high density and on a completely unsuitable diet. Don't make these mistakes!
A C Highfield
Warning: This page features some graphic images of injuries and diseases caused by innapropriate mixing of species.
If you already have one or more tortoises, you may wish to add another animal to your group (the collective noun for a group of tortoises is a 'creep', by the way). Sometimes people feel that a solitary tortoise is 'lonely' - though it is more likely that this represents projecting human emotions onto a reptile than reflecting objective reality. Most tortoises live very solitary lives, except for brief periods of contact during mating season.
There may be other reasons why you wish to do this, however, but you should carefully consider the following points before adding new animals to an established animal or group:
DISEASES
It is very important to realise that an animal may be contagious or infectious without appearing to be sick itself. It is no use therefore simply avoiding evidently ill animals - even an outwardly healthy tortoise may be carrying a disease which could be lethal to others which it contacts. Few reptile keepers (and field researchers) take such diseases seriously enough. It is infinitely safer to be over-cautious than careless. There are several broad categories of pathogens to consider:
Parasitic organisms
These include nematodes ('worms'), flagellate and ciliate protozoan organisms and ectoparasites such as ticks (these are usually only seen on freshly imported tortoises or on tortoises which have been kept in close proximity to sheep or goats). All of these parasites can cause serious difficulties by themselves, but more worrying still is their ability to act as potential vectors for other, much more serious bacterial and viral pathogens. Ticks in particular are major vectors of haemolytic pathogens.
Bacterial organisms
These include a wide range of Gram-negative organisms which can prove highly resistant to antibiotics and which are frequently implicated in the diseases of tortoises and turtles (e.g. pseudomonas, citrobacter, klebsiella, serratia and aeromonas etc.) - these are commonly isolated from such diseases as stomatitis ('mouth rot') or necrotic dermatitis ('shell rot') and from abscesses. These organisms are frequently highly tenacious and are very easily transmitted. It is not unusual for entire groups of tortoises in a collection to succumb to diseases caused by these pathogens - especially if hygiene measures are not up to standard.
A severe case of necrotic stomatitis, or 'mouth rot'. Such cases can be very difficult to treat effectively.
Mixing species, in this case Testudo ibera with Testudo hermanni can result in severe trauma injuries due to structural and behavioural differences. For example, Testudo ibera 'rams' the shell of females agressively. Hermann's tortoises do not and cannot withstand such assaults. This leads to severe physical trauma to the shell, often followed by secondary bacterial infections such as necrotic dermatitis or 'shell rot'. If untreated, this can prove fatal.
Viral organisms
Viral organisms represent an extremely serious threat. They must never be underestimated. They are not easy to detect, are extremely difficult (or impossible) to treat, and can be spread very easily from animal to animal. Specific viruses causing severe forms of stomatitis, respiratory disease, shell disease,and hepatitis in tortoises and turtles have been described in the technical literature. There can be very high mortality rates indeed from viral outbreaks in groups of tortoises, often 100%. The Tortoise Trust is aware of several cases where dozens of tortoises died following just one careless new introduction. Laboratory tests are now available to 'screen' for some, but not all, of these diseases, however, and it is certainly worth considering these in the interests of safety. Consult your specialist vet for advice.
Chelonian Herpes-Virus in a Stigmochelys pardalis (Leopard tortoise). This condition is HIGHLY contagious and has an almost 100% mortality rate.
Mycoplasma organisms
These are implicated in many outbreaks of highly contagious respiratory disease. Typical symptoms include:
Discharge from mouth and nose.
Eyes swollen or closed.
Difficulty breathing.
Decreased appetite.
Excessive sneezing, wheezing, coughing, or gasping.
Generalised depression and lack of normal activity patterns.
Basic precautions
It is wise to follow the following basic guidelines as a routine management procedure in all collections, small and large. In fact, the larger your collection and the more incoming and outgoing animals you have the greater the danger of contracting or transmitting disease. The safest collections are those which are small in number and are stable, with no new arrivals. Large collections with many mixed species tend to have the much worse overall health records than small, stable and specialised groups.
Quarantine all new arrivals for at least 18 months.
Keep quarantine animals entirely separate from all other stock and feed separately using different utensils for each.
Do not randomly mix species or animals from different geographical origins in collections.
Mixed collections tend to have very poor overall survival rates. Keeping species (and geographical sub species) separately is vastly safer. Mixing 'spur-thighed' tortoises from Turkey with those from north Africa is definitely not a good idea; there is no doubt whatsoever that where this is done the more delicate north African species suffer a much enhanced rate of disease and mortality. When kept separately there is no such problem.
It is the view of the Tortoise Trust that a combination of adopting good general hygiene measures and maintaining only naturally sympatric species in close contact makes a major contribution to the safety of any collection.
If tortoises from widely differing backgrounds are allowed to mix at random, there is no doubt that some will have no natural immunity to organisms carried normally by others. There are also profound behavioural differences in many cases, with the potential for severe injury and stress) as a result. For example, some species bite agressively, while others 'ram' shells.
Further Precautions
Always use a high quality antiseptic for cleaning food preparation surfaces, feeding utensils, accommodation and medical equipment. We recommend 'Betadine' (povidone-iodine) which has good antibacterial and even some anti-viral properties. Virkon-S is another useful product for disinfection.
Virkon-S + a Povidone-iodine solution.
Wash your hands regularly after handling all animals. Use different footwear (or overshoes) in quarantine areas.
Routine use of antseptic hand rub is highly recomended before handling different groups of animals. It is not 100% effective, but it certainly helps to reduce risk.
Remove all sick animals from the rest of the collection immediately and obtain expert veterinary treatment as quickly as possible. Where an infectious disease is suspected always commission laboratory tests to determine the nature of any pathogen. Such data could prove invaluable should the disease later spread. Some specific practices should definitely be avoided as they contribute enormously to the danger of acquiring or transmitting disease:
NEVER employ invasive treatment or study techniques (e.g. tube feeding, injections or identification tagging, marking etc.) without first ensuring that all implements are satisfactorily sterilised each and every time.
DO NOT mix large groups of tortoises from different origins together.
DO NOT overcrowd animals.
DO NOT allow large groups of animals to feed together. This is guaranteed to spread disease if any is present. Feed individually or at worst in small groups. One animal with stomatitis or a respiratory condition such as 'RNS' or Runny Nose Syndrome (see 'mycoplasma', above, for one cause of this) is enough to spread the disease through an entire collection if the animals are allowed to feed together.
BE CAREFUL when 'holiday homing' or when taking animals on breeding loan. ONE SINGLE CONTACT CAN INTRODUCE AN 'ALIEN' PATHOGEN.
MATING is also a high risk activity insofar as spreading disease is concerned. It is best to restrict mating to established small groups or pairs. Random mating should not be permitted, especially if new introductions are present.
DO NOT attend meetings with your tortoises or turtles; such gatherings are an ideal place to acquire or spread diseases. It is very difficult to ensure adequate disease precautions prevail at public meetings where large numbers of animals congregate and it takes only one careless person to infect a large number of animals.
AGE AND EGG LAYING FEMALES
Do not subject elderly females to the (usually unwelcome) attention of males. Not only can this cause severe stress, but if a female has not had eggs for many years she may now be in no condition to lay them safely. Egg peritonitis ('egg binding') is a frequent and usually fatal consequence of trying to force elderly females to breed. It is also important not to expose any female to the unwanted attention of males without places to hide and escape. Certainly having more males than females within an area is high risk, not only from the perspective of injury and stress to the females, but also male-male as a consequence of territorial combat and competition. Overcrowding greatly increases the risks of both disease and aggression.
SPECIES COMPATIBILITY
Certain species are much more aggressive in their general behaviour than others; some frequently and routinely bite for example, as noted above. Other tortoises with more restrained habits may find being subjected to this kind of behaviour extremely stressful. and may sustain serious,sometimes fatal, injuries. Always try to keep compatible and closely matched groups. This is not only better from the breeding and behaviour aspects, but it also significantly reduces the risk of disease. In addition to these factors, it is also the case that different species have different dietary requirements and different environmental needs: on all counts then, mixing species is categorically not recommended.
Biting injury due to overcrowding, increased aggression and mixing incompatible species.
Another example of a biting injury due to overcrowding, increased aggression and mixing incompatible species.
Steps to safer introductions:
IDENTIFY YOUR ANIMALS CORRECTLY
ESTABLISH THE AGES OF ANY FEMALES INVOLVED
QUARANTINE ALL NEW SPECIMENS FOR AT LEAST 18 MONTHS FIRST
DO NOT OVERCROWD TORTOISES
NEVER MIX DIFFERENT SPECIES
The Tortoise Trust can assist with identifying tortoises and in establishing ages. Please send good quality photographs of any tortoises which you require identifying.
References:
Leineweber C, Müller E, Marschang RE. Herpesviruses in Captive Chelonians in Europe Between 2016 and 2020. Front Vet Sci. 2021 Oct 13;8:733299. doi: 10.3389/fvets.2021.733299. PMID: 34722701; PMCID: PMC8549816.
To receive updates and notifications of new articles, videos and other important news please consider 'Subscribing' to the Tortoise Trust. There is even a free option available. This supports our work and allows us to make this information available. The Tortoise Trust also offers comprehensive online courses that cover all aspects of behaviour, ecology and captive care.
(c) 2024 A. C. Highfield/Tortoise Trust
Comments