Plethodon punctatus

Geographic Range

Cow Knob salamanders, Plethodon punctatus , are found on the Appalachian Mountain chain that runs through north-central Virginia and northeastern West Virginia. More precisely, Cow Knob salamanders are found on the Great North and Shenandoah Mountains. These populations are located in Rockingham County, Virginia and Pendleton County, West Virginia. Populations of Cow Knob salamanders have only been documented on mountaintops above an elevation of 732 m.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Plethodontid salamanders are often arboreal, or are mostly found in forested habitats resting or climbing on trees. Cow Knob salamanders can also be arboreal but are more commonly found underneath rocks or foraging around the forest floor. They can also be found in clusters around or inside fallen logs or live tree trunks. During episodes of dryness or high temperature, Cow Knob salamanders retreat underground or are inactive on the forest floor. These salamanders emerge during April, and generally return to deeper natural burrows underneath rocks and logs around late October. Even during warmer episodes, these salamanders are completely terrestrial, lacking an aquatic larval stage. They haven't been reported below 732 m elevation and are most commonly found in moist soils on north-facing slopes above 914 m elevation.

• Habitat Regions
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

Physical Description

Cow Knob salamanders are also known as white-spotted salamanders because of their bright white dots along the entire surface of their bodies. These spots, which can also be pale yellow, are visible even as juveniles. Below their white spots is grayish-black color that aids in camouflage. Their throats have a lighter tone and the ventral portion of their neck can also be covered in spots. They have webbed feet and 17-18 costal grooves. As adults, they measure 10-17 cm TL (total length) and 75 mm SVL (snout-vent length), and weigh just over 5 g. Individuals are considered adults once males reach a SVL of 49 mm and females reach a SVL of 59 mm. Males have a mental gland located in the lower jaw that is used for pheromone secretion, therefore sexes are not always alike. These salamanders also lack an aquatic stage, do not possess gills, and are completely terrestrial.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes shaped differently

Development

Cow Knob salamander eggs are laid loosely underground and hatch either during spring or early fall. Exact time before hatching has not been reported but is most likely around a month. Salamanders in the genus Plethodon exhibit direct development, looking similar to a small adult at hatching. Studies in red-backed salamanders, Plethodon cinereus , exhibit a short gilled phase, but lose these larval features before hatching. Therefore, no metamorphoses takes place. Once hatched, juveniles essentially look like smaller adults and are largely independent, reaching sexual maturity in about three years after hatching. Females are sexually mature at a SVL of 59 mm, and males at a SVL of 49 mm. Larval stages are much slower in plethodontids, growing about 1 mm per month in this stage. Like other salamanders, Cow Knob salamanders exhibit indeterminate growth. The SVL and general size of the salamander can be used to determine sex, but most sex identification is determined through the presence of a mental gland which only males possess.

• Development - Life Cycle
• metamorphosis metamorphosis
• indeterminate growth indeterminate growth

Reproduction

Male Cow Knob salamanders possess a mental gland that secretes pheromones. The pheromones are used in mating, inter- and intra-species recognition, and establishing territories. Male Cow Knob salamanders use these pheromones to accurately signal a female for mating. Once signaled, the courtship session begins and can last for more than just one mate exhibiting promiscuous behavior. These salamanders are polygynandrous, therefore multiple males can mate with multiple females. Due to a lack of an intromittant organ, male Cow Knob salamanders inseminate females with the use of spermatophore. Males deposit a spermatophore external to the female; through a special straddle-walk courtship maneuver, she sits on it to take it in through her cloaca, ensuring internal fertilization.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

When Cow Knob salamanders are above ground during wetter periods, like the spring and fall, mating likely occurs. There have been findings of clusters of adults, both male and females, under rocks during dryer or colder periods, but the evidence is insufficient to suggest that they mate primarily during this time. Most fertilization is believed to occur during the fall months, and egg-laying usually takes place at the start of spring. However, there are accounts of some mating that occurs during spring. The eggs are laid in summer where they hatch and then join the forest floor surface during the start of fall (September). This spring mating is less common but can still happen. Female salamanders generally 7-16 eggs. However, it is unknown how long the eggs take to hatch, and how big they are at hatching in Cow Knob salamanders. In both males and females, sexual maturity is gained at about three years after hatching, when the females have an SVL of 59 mm and the males have an SVL of 49 mm.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

No specific nests have been reported for this species of salamander but there sources suggest that these salamanders deposit their eggs beneath rocks or underground. Juveniles generally follow adult males and females and forage for food alongside them for their first three years. However, it’s unclear whether the adults are the parents or just among a group of adults in the area. Because of the polygynandrous nature of these salamanders, it’s likely that direct parental care is minimal.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Cow Knob salamanders are not kept in captivity. In the wild, the lifespan of these salamanders is unknown but is most likely to similar to other species in the Family Plethodontidae, which is around 15 years on average. There are no diseases reported for this species and most of their population loss is most likely due to climate change. The only other possible limiting factor of a longer lifespan, would be the presence of parasites in the species but there are no reports stating how many of these salamanders are affected and to what degree.

Behavior

Cow Knob salamanders tend to be more social in their everyday life and move around frequently during the day when in a cooler or moister environment. These salamanders are most active on the forest floor but can burrow in times of warmer/dryer weather and can even climb trees. During warmer, dryer seasons, Cow Knob salamanders can be seen in clusters within burrows or underneath rocks and logs. There is also evidence that they go into hibernation in extreme cold, specifically from November to March. When above ground, they still remain social, but generally forage or hunt in smaller groups or even alone. Pheromones secreted by the males' mental gland are used as a form of communication, especially in courtship. In courtship, these pheromone signals are secreted by the males to attract females and begin mating with one another for what can be multiple sessions among multiple mates. A unique straddle-walk maneuver is also used during courtship that helps the females locate the males' spermatophore. As juveniles, these salamanders tend to follow adults for about three years until sexually mature before hunting and foraging independently.

• Key Behaviors
• scansorial
• terricolous
• fossorial fossorial
• diurnal diurnal
• motile motile
• hibernation hibernation
• social social

Home Range

Cow Knob salamanders generally hunt, forage, and mate within close proximity to their burrows. These activities occur almost exclusively above ground on the forest floor or even in trees as they are scansorial as well. They can be territorial with the use of pheromones and often mark burrows or other objects along the forest floor. Territory size has not been accurately reported but Lannoo (2005) does suggest that these salamanders only move a few meters away from their home in their lifetime. Buhlmann et al. (1988) found individual movements ranged from less than 2m to a high of 17.4 m.

Communication and Perception

Juvenile Cow Knob salamanders generally take 3 years to fully develop, but exhibit the same sort of perceptual skills as their adult counterparts. Moisture seems to be the biggest queue for aboveground activity. Both juvenile and adult Cow Knob salamanders retreat underground or undercover during dryer/warmer periods. They can be seen clustered together during this time of retreat and it is possible that mating occurs during this time. During periods of rainfall, Cow Knob salamanders emerge to forage. Male salamanders of the genus Plethodon also use pheromones for territorial and mating use. These pheromones are secreted through the mental gland, which is a small sac-like gland located in the male's neck region. Although Cow Knob salamanders rely heavily on chemical signals for communication, common uses of touch and vision are identified when foraging for food and sensing their surroundings when in clusters. Tactile signals are also used in courtship when the male deposits his spermatophore on the ground where the female then sits on it.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Moisture of the air and forest surface affects the feeding microhabitats for Cow Knob salamanders. During dryer/warmer periods, it is believed that these salamanders hunt or forage underground or under leaf litter. In wetter conditions, Cow Knob salamanders hunt on the forest surface. Most of their energy consumption occurs during this wetter period. They spend this time hunting a variety of invertebrates like arachnids (spiders and mites). They eat myriapods like millipedes and centipedes. They also eat insect adults and larvae, including those from the orders Coleoptera, Orthoptera, Diptera, and even non-insect hexapods like collembolans. The size of prey depends almost exclusively on the size of the salamander.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods

• Animal Foods
• eggs
• insects
• terrestrial non-insect arthropods

Predation

There isn't much research done on the predation of Cow Knob salamanders but they are most likely hunted by the same sorts of animals that prey on other species in the Family Plethodontidae. Petranka (1998) suggests small birds, shrews, woodland snakes, skunks (Family Mephitidae), and Virginia opossums ( Didelphis virginiana ) are the most likely candidates for predators. These salamanders have some potential camouflage, but it's most likely not very useful because they're covered with white spots over their grayish/brown skin. There could be possible scenarios where they can camouflage very well especially if they're near pebbles or rocks on the forest floor.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Cow Knob salamanders serve as opportunistic prey to nearby predators. They serve as a host to parasites in their digestive tract. Only two parasites have been reported: a protozoan ( Cepedietta michiganensis ) and a nematode ( Batracholandros magnavilvaris ).

Economic Importance for Humans: Positive

There are no known positive economic effects of Cow Knob salamanders on humans.

Economic Importance for Humans: Negative

There are no known negative economic effects of Cow Knob salamanders on humans.

Conservation Status

Cow Knob salamanders are listed as "Near Threatened" on the IUCN Red List. They have no special status on CITES and State of Michigan list. Although acknowledged as a "species at risk" by the US Fish and Wildlife Service, they are not federally listed. The Virginia Wildlife Action Plan lists these salamanders as a Tier I species, meaning they require the highest amount of conservation efforts. They are a species of special concern in West Virginia.

The primary threat to Cow Knob salamanders is potential climate change in the future. These salamanders inhabit mountaintops with a cool, moist habitat. Rising global temperatures could affect this, and migration to higher elevations or northward is not an option for these salamanders. Timber harvesting can also affect their habitat. Relatedly, invasive species that defoliate forests and cause significant tree mortality include gypsy moths ( Lymantria dispar ) and hemlock woolly adelgids ( Adelges tsugae ). Both insect species indirectly harm Cow Knob salamanders by habitat loss or alteration.

Local efforts have been made by the George Washington National Forest (Virginia) as land managers recognize that this is a sensitive species. Most of the land above 914 m in this forest has been allocated for forest management and is closed off to the public. This includes 234.7 square km of Cow Knob salamander habitat that is currently being recommended to Congress to be recognized as a National Scenic Area. Researchers suggest that additional studies into the elevational limits of this species be examined, especially in light of predicted climate change.

Additional Links

AmphibiaWeb

Encyclopedia of Life

Contributors

Gabriel Hessler (author), Radford University, Logan Platt (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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