The alpine salamander (Salamandra atra) is a black salamander that can be found in the Alps, and through the mountainous range in Europe. It is a member of the genus Salamandra. The species name, atra, is derived from the Latin ater, meaning dull black. The colour of salamanders has evolved over time, as some species are completely monochrome black, and others have yellow spotting and marks. Their life expectancy is at least 10 years. There are four subspecies of the alpine salamander, with varied distribution and physical colour. Unlike other salamanders, whose larvae develop in water, the alpine salamander and its subspecies are fully terrestrial species in life and gestation. They give birth to live young.
Alpine salamanders produce toxic compounds from their skin. These compounds may protect them from both predator and microbial threats.
Description Alpine salamanders are often small in size, and dark brown or black. Members of the subspecies are not wholly black or brown monochrome, but rather have mosaic or spotted patterns. Members of the subspecies Salamandra atra aurorae have bright splotches on its dorsal side and head. The colour is often bright yellow, but can range to shades of white or even grey. Distribution of the pigment is dependent on the distribution of certain cells, so may be smooth and even or patchy.
Female S. atra tend to be larger than the males, and can grow up to . Males will grow to around ; both measurements include the tail. Males have swollen, visible cloacae, and are slenderer than females. The salamanders have parotid glands posterior and lateral to their eyes, giving them an elongated head shape. They tend to have between 11 and 13 costal grooves along the sides of their bodies, and a double row of dorsal glands runs down their backs on either side of their spines, down to the tips of their tails.
Colour Most alpine salamanders that are either completely black (melanistic) or predominantly black have the dark pigment as a baseline, but the evolution behind this dark colouring has a winding history. Scientists have studied the hypothesis of if the salamanders start completely black, or if they evolved like that over time. DNA-evidence traced through maternal lineages suggest the latter, that salamanders evolved their black colour over time.
Biological pigmentation is determined by presentation of specific pigment-producing cells, called chromatophores, which absorb and/or reflect light in a particular way to then appear as a colour. In S. atra, there are different cells present or activated, which yield different colours; melanophores contribute to the dark colour by producing the dark pigment melanin, while xanthophores produce a yellow pigment, and iridophores are simply light-reflecting. The fully black phenotype seen in S. a. atra results from the salamanders' melanophores in the dermis and epidermis, producing melanin alone. Xanthophore-iridophore complexes are responsible for production of yellow spotting, which appears bright. In species without yellow patches, it appears that they do not ever develop these cells. In S. a. aurorae or other salamanders with different colour on different parts of their body, two distinct skin types are present; one that only contains melanophores (black), and one that has melanophores, xanthophores, and iridophores in combination.
The yellow colouring on some alpine salamanders is thought to be an aposematic strategy to fend off predation. The pure black colouring is also suggested to be a form of thermoregulation, though it may also be considered a warning to some predators.
Taxonomy and subspecies
S. a. atra is a fully melanistic (black) subspecies from the Central, Eastern and Dinaric Alps. This subspecies is the most widespread. S. a. aurorae, the golden alpine salamander, has golden or yellow spots on its back and primarily lives in a small area in the Venetian Prealps near Asiago, and in the Italian Alps.Bonato, Fracasso. Movements, distribution pattern and density in a population of Salamandra atra aurorae (Caudata: Salamandridae). 2003. Amphibia-Reptilia 24: 251-260. S. a. pasubiensis, with fewer yellow spots than S. a. aurorae, lives in a different part of the Venetian Prealps. S. a. prenjensis lives on Prenj Mountain, part of the Dinaric Alps in Bosnia and Herzegovina. The validity of this subspecies is yet to be confirmed, and some scientists in the field debate if this salamander should be considered its own independent species.Bonato & Steinfartz. Evolution of the melanistic colour in the Alpine salamander Salamandra atra as revealed by a new subspecies from the Venetian Prealps. Italian Journal of Zoology 2001, 72, 253-260.
Genetic analysis suggests that the Corsican fire salamander (Salamandra corsica) is the closest related species, and that the black-yellow colour is an ancestral feature of alpine salamanders. Proposed colonisation from south (Prealps) to Alps was by the fully melanistic (derived feature) S. a. atra after the last retreat of the ice sheets.
Habitat and distribution
Habitat As terrestrial organisms, these salamanders live on land. S. atra tend to live underneath stones or logs, or in rocky crevices in their mountainous habitat. They also are diurnal, and most active in the day with periods of inactivity, rest, or sleep at night. They will engage in nocturnal activity on a weather-dependent basis. Ideal weather for alpine salamanders is rainy or post-rain, at temperatures between .
Geographic distribution The alpine salamander is found from the France–Switzerland border at the western end of its range, all the way through Switzerland and Austria to the Dinaric Alps at the eastern edge of its territory. It typically lives at altitudes above above sea level, even reaching altitude. The western Alps (in France and Italy) are inhabited by a similar species, Lanza's alpine salamander (Salamandra lanzai), in only one small area. S. atra generally live in forested biomes, particularly deciduous-coniferous mixes. They also can inhabit meadows or grasslands in the mountains, and tend to do well with a mix of tree types.
Their range spans several nations, including Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Kosovo, France, Italy, Austria, and Switzerland.
Home range and territoriality
They thrive in forest environments that have silver fir and beech trees. Coniferous forests that have high proportions of Norway spruce and European larch trees also provide adequate habitats, even though the salamanders live on the ground floor. Because alpine salamanders are completely terrestrial, they have on-land territories that they tend to return to throughout the day and for refuge. They often return to the same sites for much of their lives. Whenever they leave their sites, they expose themselves to predation and also to the chance of losing their site. Alpine salamanders are ectothermic, so losing a refuge or shelter could leave them exposed to the elements and be extremely costly, if not fatal, due their lack of an internal thermoregulation mechanism.
This high dependency on a quality nest site supports the theory that many terrestrial salamanders, including S. atra, engage in territorial behaviour. Capture-recapture methods suggest that the species is very stationary; was the maximum observed distance traveled by one individual during the summer season. About 120 individuals per hectare were counted in most suitable areas with over 2000 individuals per hectare also observed, suggesting that this rather cryptic species is quite abundant.
Territorial behaviour They employ scent-marking techniques for territorial behaviour, and to mark their territories using faecal pellets so they can identify their own shelters. Scent-marking is an intra-species communication, where chemical signals convey specific messages to other S. atra individuals. Alpine salamanders can determine if a faecal pellet they find has been left by a member of their same sex and/or species. Thus, this technique serves a double purpose to warn other salamanders that that particular location has already been claimed.
Females are more likely to return to their home site, while males are more emboldened to enter another male's territory. Their faecal pellets allow them to both participate in homing behaviour, or returning to their own site, and territoriality, and determine intruders on their territory or invade the spaces of others.
Conservation
Alpine salamanders are not resilient to habitat changes (few terrestrial salamanders are), so risks of climate change altering their living spaces is severe. Although alpine salamanders are listed as Least Concern on IUCN Red List, their numbers are decreasing. Additionally, some subspecies of S. atra are in greater danger. Population numbers are declining in S. a. aurorae.
One of the greatest dangers to alpine salamanders overall is commercial deforestation in their habitats. Machinery like tractors or other forestry tools can compress the soil, eliminating some of the small insects that S. atra eat or eliminating potential nooks and burrows for them to use as shelters. Many scientists propose changes in the timber industry as an attempt to heal these habitats. The salamanders may also change their morphology as global temperatures rise. Amphibians and other organisms that do not internally regulate their body temperature may need adaption mechanisms to remain at ideal physiological temperatures in the face of changing climates. Other issues like acid rain or precipitation changes could prompt many animals, including alpine salamanders, to be forced out of their habitat. Alpine salamanders play a crucial role in their ecosystems. There are already animal and ecosystem conservation laws in Europe, but many scholars recommend additional ones to protect the flora and fauna.
Predators Due to their toxicity, as well as decreased concentration of animals at high altitudes, researchers are unsure of consistent predators for alpine salamanders with limited observation. These salamanders do move slowly, which could increase their risk of being caught. Generally, predators of the broad category of toxic Salamandra species can include birds, rats, and snakes, as well as other, larger carnivorous mammals like raccoons, mink, wild boar, and foxes.
One notable predator of S. atra is young snakes. In particular, juvenile European adders (Vipera berus) pose a risk because they live at similarly high altitudes to alpine salamanders. S. atra has been suggested to make up just under half of these snakes' diets in some locations. They may hunt for alpine salamanders during early morning hours, when S. atra is most active. There also has been evidence of these snakes recorded swallowing alpine salamanders. V. berus, alongside the grass snake (Natrix natrix), are noted predators of alpine salamanders in the Italian Alps.
Feeding Male and female alpine salamanders have relatively similar diets. Some specific organisms they prey on include species such as beetles, snails, millipedes, and spiders, but alpine salamanders display preferences among prey. S. atra typically consume organisms from the Coleoptera and mollusca taxa. These taxa are the most crucial component of their diet. They also tend to eat larger prey since they themselves are larger salamanders. Such preference indicates a dimensional selectivity, in which the energy intake of prey consumption is maximised. Though alpine salamanders have definite dietary preferences, they have a substantial amount of variation in their diet that corresponds to their own optimal physical needs and prey-catching abilities.
Mating and interactions
Mating pattern