top of page

Cusp formation

in European tortoises

Die nachfolgenden Ausführungen zum Thema Höckerbildung wurde von mir bereits im Jahr 2003 veröffentlicht. In den nachfolgenden Jahren habe ich das Phänomen eingehend erforscht. Das zusammengefasste Ergebnis wurde im September 2021 im TESTUDO, der Vereinszeitschrift der Schildkröten-Interessengemeinschaft Schweiz (SIGS) veröffentlicht. Ein PDF des Artikels befindet sich am Ende dieses Berichtes.

Thb mit ausgeprägten Höckern in menschlicher Haltung auf einem Wiesengelände im Garten.

In the vast majority of European tortoises reared in human care, pyramid-shaped bone plates develop in the center of the horny shields of the dorsal armor.

The reasons for the formation of these bumps have not yet been scientifically proven.

I want to briefly present my findings on this phenomenon here.

  First of all, you should refrain from the idea that all turtles must be grown equally. This is pure wishful thinking from us turtle owners. There is no such thing in nature either. In the wild, turtles with humped and misshapen shells can be found in every population. It doesn't always have to be pathological. Completely smooth and  Evenly grown turtle shells can only be found today in habitats that are really original and largely unchanged by humans. 

Smooth-grown Dalmatian tortoise in a river valley in Croatia.

Glatt und ebenmaessig gewachsene Thc in Dalmatien..

Thboettgeri growing evenly but with bumps in Greece.

Ebenmaessig aber leicht hoeckerig gewachsene Thb in Griechenland.

Smooth but misshapen thboettgeri in Greece.

Glatt aber unfoermig gewachsene Thb in Griechenland.

Smooth but extremely tall Thhermanni in Tuscany.

Glatt aber extrem hoch gewachsene Thh in der Toskana.

A slight hump as such is initially not necessarily pathological on its own and does not cause any impairment to the animal.


How do these humps arise?

It is generally assumed that the humps have something to do with keeping the soil in too dry a substrate.

However, through my long-term observations in the wild, I have come to the conclusion that the mere formation of humps cannot only have to do with the ambient and air humidity, but rather must be due to the actual water balance of the turtles. 

Basically, turtles only live in habitats with high humidity.

I regularly find mostly smooth-grown animals in populations that live in habitats with free access to water.

Munched turtles are mainly found in areas where there are no streams or other water points. There is always a high level of humidity in these habitats.

I found extremely humped animals in a very dry, arid, extensive coastal habitat on Sardinia. The water situation there has become so worsened in recent years due to the lack of rain that hundreds of turtles literally dry up every year. Even an extremely dry summer is enough to induce cusp growth in the bone carapace in young animals.

Thhermanni died in Sardinia due to lack of water.

Panzer einer vertrockneten Thh auf Sardinien..jpg

I know owners who used to keep their animals in dry substrate and low humidity and still reared turtles with smooth shells. However, these keepers regularly bathed their hatchlings and the growing turtles, which enabled the animals to balance their water balance.

So in principle it should be sufficient for smooth shell growth if the turtles regularly take in enough water. Based on my experience and observations, the pure ambient and air humidity cannot have any influence on the formation of bumps.


However, especially for young turtles (of course also for older ones) a moist substrate and especially high relative humidity are still essential. It is well known that turtles also absorb moisture through their skin. The high humidity is always present in all turtle habitats and is also extremely important for the respiratory organs.

In nature, and in principle also with us, this mere hump formation, caused by a lack of moisture, would not in itself be harmful to the health of the animals.

But now comes the other side of the coin, as you can see very impressively in these two carapaces, which have been sawn open lengthways.

Aufgesägter Knochenpanzer eines Wildtieres
Dampfaufzucht Thb

I “prepared” the left tank in Sardinia for illustrative purposes. It comes from the above-mentioned area close to the sea and therefore very humid. Although the carapace has a relatively strong hump, the active column has grown normally and no health damage is to be assumed.   The right tank belonged to a “steam rearing” who died far too young and was fed wrongly with animal feed. The spine is also damaged by this extreme hump.  


The real problem is not the bare humps, but the additional, often wrong, protein-rich diet in human care and the lack of water from which many kept animals suffer. About 70% of the total body substance in turtles also consists of water. Ultimately, all life processes take place in an aqueous medium. Even a 10% loss of body fluid can result in metabolic disorders.

Just having a bowl of water does not necessarily mean that the animals will consume enough water.

Unfortunately, this is a problem that is hardly noticed because it is little known!

Since the food here cannot in any way be compared with the plants in the turtle habitats, our turtles need significantly more water than their conspecifics in the south for healthy growth.

The pathological hump growth only occurs when European tortoises are not kept in a species-appropriate manner and are naturally fed.

You can read in detail what kind of animal welfare and natural feeding means in my two books

Read "Natural keeping and breeding of the Greek tortoise" and "Forage plants" .


I would like to emphasize two points at this point.

1. European tortoises are pure herbivores and should not eat protein-rich food of animal origin. This is particularly true for the growing juvenile turtles. In untouched, original habitats, European tortoises do not eat meat or carrion, but rather eat a balanced diet of plant-based food. Exceptionally, turtles in changed habitats only eat meat to compensate for a nutritional deficiency in minerals or vitamins, such as calcium, iron, zinc or vitamin D. they cannot obtain from the vegetable food available to them. If your turtles often specifically eat snails or worms, rethink your feeding plan and expand the range of suitable forage plants .

2. A strong day / night temperature gradient is also essential for the health of European tortoises. In the habitats this temperature difference is regularly 20 degrees and more!

Yes, you read that right, twenty degrees.

Why this is so and what negative effects  has a smaller day / night temperature gradient for the turtles, you can also read in my books “Natural keeping and breeding of the Greek tortoise” and “ European tortoises, habitat and way of life ”.

Evenly smooth Greek tortoises in a primeval macchia habitat in Albania and North Macedonia.

Klicken Sie auf das nebenstehende PDF und lesen Sie die eingangs erwähnte Zusammenfassung meiner Forschungen zum Thema Höckerwachstum und Panzerdeformation bei Europäischen Landschildkröten. Veröffentlicht wurde der Artikel im September 2021 im TESTUDO, der Vereinszeitschrift der Schildkröten-Interessengemeinschaft Schweiz (SIGS).

Der Artikel unterliegt dem Urheberrecht und darf ohne schriftliche Genehmigung des Autors und des Verlages nicht reproduziert oder anderweitig veröffentlicht werden.

bottom of page