What influences colour patterns in chameleons

What influences colour patterns in chameleons

by Alex Negro Science

Chameleons are known for their ability to change colour. International scientists have now investigated what exactly influences different colour patterns in different populations. They want to know to what extent the habitat itself, the distance to other populations or social interactions influence the colour change.

The test subjects were European chameleons (Chamaeleo chamaeleon) caught in La Herradura and Sanlúcar in Spain. The two regions are around 230 kilometres apart. Other Chamaeleo chameleon were collected in the north-western Negev and on the Carmel coast in Israel (around 180 km apart). On the other hand, flap-necked chameleons (Chamaeleo dilepis) were captured in Simbithi, Zulu Falls and Maduma Boma in South Africa. The three locations are between 100 and 550 kilometres apart.

Each chameleon was subjected to two experiments. In the first, the scientists let the chameleon walk two metres on a horizontal stick, which was placed in the sun about one metre above the ground. In the second experiment, a second chameleon of the same species was placed on the same stick 50 cm away from the first. The colour patterns shown by the animal during the experiments and its behaviour were recorded for 20 minutes. The data was then analysed using computer programs. Blood was taken from a cut claw of all chameleons and genetically analysed. The habitats and soil conditions were also analysed in various ways and statistically evaluated. The captured animals were kept in ventilated plastic cages for a maximum of 12 hours and released after the analyses. Unfortunately, the study does not mention how many chameleons were caught and released in total.

As expected, it turned out that the individual populations of both the European and the flap-necked chameleon differed genetically from each other. The populations of Chamaeleo dilepis had significantly different haplotypes.

In the flap-necked chameleon, the females were significantly larger than the males in two locations, but not in Simbithi. The scientists also found that the colour patterns of the three populations studied could be clearly distinguished from each other. They concluded from the results that the colour patterns in Chamaeleo dilepis are primarily dependent on genetic isolation. The habitat itself and the size of the chameleons did not influence the colour patterns.

In the European chameleon, however, the situation was different: Body size and genetic distance to other populations predicted colour patterns in males very well. However, the colour patterns were independent of the location where the animals were found. Soil or vegetation colours only had a minor influence on the colour of females.

Genetic and behavioural factors affecting interpopulation colour pattern variation in two congeneric chameleon species
Tammy Keren-Rotem, Devon C. Main, Adi Barocas, David Donaire-Barroso, Michal Haddas-Sasson, Carles Vila, Tal Shaharabany, Lior Wolf, Krystal A. Tolley, Eli Geffen
Royal Society Open Science 11: 231554
DOI:  0.1098/rsos.231554

Knysna dwarf chameleons: city vs. forest habitat

Knysna dwarf chameleons: city vs. forest habitat

by Alex Negro Science

How do chameleons change when their natural habitat has to make way for human settlements? International scientists recently got to the bottom of this question. They hypothesised that a chameleon living in a suburban area must differ from its forest-dwelling conspecifics in terms of injury frequency, external characteristics and bite force as an expression of changed living conditions.

Between 2020 and 2022, 276 Knysna dwarf chameleons (Bradypodion damaranum) were studied in South Africa. The locations chosen were George and Knysna, two towns located around 60 kilometres apart on the south coast of South Africa. George was founded in 1811 and now has over 220,000 inhabitants, while Knysna was founded in 1825 and currently has just under 76,000 inhabitants, although they live in much less space and are therefore much more densely populated. In both cities, Bradypodion damaranum were caught in urban environments (private gardens, public parks, roadsides), examined and then released. Chameleons were also studied 10 to 12 kilometres away in their natural habitat (temperate forest). The adult chameleons were measured and photographed. The data was analysed and compared using various methods. Wounds, scars and bone fractures visible to the naked eye were counted as injuries. To measure bite force, the animals were each encouraged to bite five times on a special piezoelectric measuring device.

The analysis showed that the dwarf chameleons in urban environments had significantly lower casques and shorter gulars. The males from the city, however, had larger and wider heads. The female dwarf chameleons from the forest had significantly larger casque spurs. The males in the city had significantly more injuries (88.1%) compared to the males in the forest (72.5%). In the city, the dwarf chameleons also bit harder than in the forest when casque height and parietal crest were included in the calculations. However, when snout-vent length was included instead, there was no difference in bite force.

Differences between urban and natural populations of dwarf chameleons (Bradypodion damaranum): a case of urban warfare?
Melissa A. Petford, Anthony Herrel, Graham J. Alexander, Krystal A. Tolley
Urban Ecosystems 2023
DOI: 0.1007/s11252-023-01474-1

Panther chameleons in Madagascar

Panther chameleons in Madagascar

by Alex Negro General topics Verbreitung Newspaper articles

In the bi-monthly magazine of the DGHT e.V., the Elaphe, a nice article on the panther chameleons of Madagascar has been published. It was written by two members of the AG Chamäleons who regularly travel to the island.

The article describes in words and pictures the distribution area of the panther chameleons on Madagascar, which extends over the northern half of the island, more precisely from a few kilometres south of the village of Ankaramibe in the northwest to the north of Madagascar and down the east coast to about 90 km south of the port city of Toamasina. The chameleons are found mainly in secondary vegetation in open landscapes, but also in cocoa plantations, overgrown gardens and rainforests.

The life cycle of the panther chameleons in Madagascar is mainly determined by the rainy season between November and March. The chameleons mate during this time. After 30 to 40 days, the females lay between 11 and 35 eggs in a nest they have dug themselves. The young hatch only in the next rainy season.

The article goes into particular detail about the different local forms, the different colour appearance of the male panther chameleons depending on the location. The authors currently count more than 30 different local forms on Madagascar, which are separated from each other by natural barriers such as rivers. There are probably many more, but not all of them have been discovered yet.

Pantherchamäleons (Furcifer pardalis) – Meister der Farben
Thorsten Negro and Alexandra Laube
Elaphe 3, 2023, pp. 12-25

Photo: Panther chameleon of the local form Ambanja on Madagascar, photographed by Thorsten Negro.