MARBLED SALAMANDER

Ambystoma opacum
 
INTRODUCTION

Marbled salamanders are one of two species of mole (Ambystomid) salamanders that have been detected in Rhode Island. Mole salamanders are fossorial, therefore they are rarely observed above ground, with the exception of their brief breeding season. A much more common congener, spotted salamander (Ambystoma maculatum), is widespread and found throughout the state. In contrast, marbled salamanders have a relatively limited distribution; they are primarily restricted to western and southern portions of the state.
The marbled salamander is a peculiar member of the amphibian community in Rhode Island. It is the only species that breeds in the fall, whereas, all other species breed in the spring or summer (Klemens 1993). Based on our fieldwork in Rhode Island, marbled salamanders tend to prefer large, undisturbed tracts of forest, although we also detected this species in a large forested tract of land in Warwick (Paton and Egan 2001). Klemens (1993) also found marbled salamanders were more prevalent in rural areas of Connecticut, however, he also collected some individuals in suburban and urban areas.

 
IDENTIFICATION
  • Marbled salamanders are the only black and white salamander in Rhode Island.
  • Adults are moderately sized, as their total length is about 7-11 cm [3-4"] (see specific details below).
  • Their body is black, with white or light gray crossbands on the head, back, and tail.
  • Dorsal crossband colorations differs between genders, males have silvery white crossbands, whereas those of females are silvery gray.
  • Gender is best determined just prior to breeding (August), when adult males have swollen cloacal glands, which have a squared off appearance. In contrast, the cloaca of females tends to be more rounded. After males deposit spermatophores, the cloacal protuberance of males subsides and is less obvious.
  • There are 11-13 costal grooves.
  • The venter is uniformly bluish-black or brownish-black.
  • There is much individual pattern variation. B. Shoop and T. Doty (pers. comm.) have been photographing marbled salamanders for 10 years to keep track of individuals at a breeding pond in western Rhode Island.
  • Partially albinistic larvae have been reported once in Tiverton, Rhode Island (Deegan et al. 1998), which possessed integumentary xanthophores and orbital melanophores.
  • Hatchlings are blackish and rather drab and have pond-type morphology with bushy gills and dorsal fins that extend almost to the front limbs (Petranka 1998a).
  • Marbled salamander larvae have a larger head, a higher dorsal tail fin, and more pointed tail than those of spotted salamanders.
 
SIZE
AGE / SEX
SVL (SNOUT VENT LENGTH) (cm)
SAMPLE SIZE

AVERAGE

RANGE

Std. Deviation

ADULT FEMALE

6.0

4.4- 7.4

0.6

210

ADULT MALE

5.4

4.3- 6.7

0.5

158

JUVENILE

4.12

3.0- 5.2

0.6

14

METAMORPH

3.6

2.3- 5.0

0.4

254


AGE / SEX
TL (TOTAL LENGTH)
SAMPLE SIZE

AVERAGE

RANGE

Std. Deviation

ADULT FEMALE

10.6

8.2- 13.2

0.9

210

ADULT MALE

9.7

8.0- 11.9

0.8

158

JUVENILE

7.4

6.2- 8.5

0.7

14

METAMORPH

6.4

3.8- 8.0
0.8

254


AGE/ SEX
MASS (g)
SAMPLE SIZE

AVERAGE

RANGE

Std. Deviation

ADULT FEMALE

8.0

3.4- 12.3

1.5

176

ADULT MALE

5.5

3.2- 8.6

1.2

112

JUVENILE

3.1

2- 4.1

0.9

5

METAMORPH

1.5

0.5- 3.1

0.42

239






 
RELATIVE ABUNDANCE
Rhode Island
During surveys we conducted at breeding ponds west of Narragansett Bay, marbled salamanders were somewhat uncommon, as they were detected at only 6 of 119 ponds (Paton and Egan 2001). . Marbled salamanders are less likely to occur in suburban or urban areas- they are most common in the rural western part of the state (Deegan et al. 1998). Our fieldwork suggests they prefer landscapes that are dominated by forests (Paton and Egan 2000).
Regional
In Massachusetts, which is at the northern limits of their range, the species has been put on the state list of rare and endangered species (Klemens 1993). In contrast, they appear to be widespread and relatively secure in Connecticut and western Rhode Island (Klemens 1993), although somewhat localized in their distribution. In addition, they are still relatively common on eastern Long Island and lower Westchester County, New York. DeGraaf and Yamasaki (2001) list them as uncommon in New England.

Marbled salamanders are one of the primary species investigated at Rainbow Bay, South Carolina, where Semlitsch et al. (1996) have been studied amphibian community structure for over 16 years. The study documented tremendous interannual variation in population sizes and productivity. The number of breeding females captured annually ranged from none to over 600, whereas the number of metamorphs emigrating from ponds ranged from none (4 out of 16 years) to almost 9000.

 

 
DISTRIBUTION
Rhode Island
Somewhat uncommon, mainly restricted to the western and southern portions of the state. We detected marbled salamanders at 6 of 119 randomly selected ponds in the mainland area west of Narragansett Bay (Paton and Egan 2001). Tom Doty and Bob Shoop monitored the population dynamics marbled salamander at one breeding pond on the Alton Jones Campus in western Rhode Island throughout the 1970s (Doty 1978) and during the 1990s. The number of breeding adults has fluctuated throughout the years, but never been extirpated (T. Doty, pers. comm.).
Regional
Marbled salamanders are at the northeastern limit of their range in New England. They occur from extreme southeastern New Hampshire (Hoopes 1938), southeastern New York, and central Massachusetts southward through the rest of New England (Klemens 1993). In Connecticut, they are found throughout the state, but tend to be absent from high elevations (above 1,100 ft [ 336 m] and most calcareous areas (Klemens 1993). In New York State, marbled salamanders have been documented on Long Island, Staten Island, and southeastern mainland counties northward to the vicinity of Albany (Klemens 1993). Only one specimen from Vermont and two specimens from New Hampshire have been collected (Taylor 1993).
General
Marbled salamanders occur throughout much of the eastern deciduous forest from southern New England to northern Florida and westward to the tallgrass prairie (Petranka 1998a). They appear to primarily be a species of southeastern North America, as their populations reach very high densities there (Semlitsch et al. 1996). They are absent from many areas including portions of the Appalachian Plateau, central Ohio, central Indiana, most of Florida, southeastern Georgia, and coastal Louisiana (Klemens 1993). Disjunct populations occur along the southern Great Lakes and in Missouri.
 
HABITAT NON BREEDING
During the non-breeding season, marbled salamanders are sometimes found under logs and rocks. They are fossorial, so they probably hibernate in deep burrows, such as old shrew (Sorex spp.) burrows. We occasionally captured adult marbled salamanders in early June near breeding ponds, but they are generally only caught from Aug-Oct. Unfortunately, little is known about their habitat requirements during the non-breeding season in Rhode Island, or elsewhere for that matter.
 
HABITAT BREEDING

In Rhode Island, marbled salamanders typically breed in ponds found in mixed deciduous or coniferous forest stands (e.g., both white pine (Pinus strobus) and pitch pine (Pinus rigida). This species appears to prefer dry, friable soils including sand and gravel deposits, as well as rocky slopes, although they are sometimes found in low-lying swampy areas (Klemens 1993). Marbled salamanders are thought to inhabit somewhat drier areas than other species of Ambystoma (DeGraaf and Yamasaki 2001); however, in Ohio they are usually found in swampy forests (Ptingsten and Downs 1989). Breeding occurs in temporary wetlands, including wooded swamps, kettle ponds, and along river floodplains. In Rhode Island, such sites generally contain red maple (Acer rubrum) and pin oak (Quercus palustris) (Raithel unpubl. data).

In addition to needing extensive forests, the presence of sphagnum moss in the pond basin is possibly another important habitat characteristic useful for detecting potential breeding ponds. Egg masses are generally deposited under sphagnum in dried-up pools and guarded by females until ponds until water levels inundate the eggs (T. Doty, pers. comm.).

 
HYDROLOGY
Marbled salamanders tend to be most abundant in temporary ponds, which dry out completely each season. Such sites usually do not have much standing vegetation and are shared commonly with wood frogs (Rana sylvatica) and to a lesser extent with spotted salamanders (Ambystoma maculatum) (Raithel unpubl. data).

 
MOVEMENT CHRONOLOGY

In Rhode Island, adults start to immigrate to breeding ponds around 1 August. Adults are generally only active on rainy nights. The majority of adults are at breeding ponds by 26 August, with some stragglers arriving as late as 10 September (Paton and Crouch In press). Males often court females before arriving at the nesting sites and males often arrive at the ponds from a few days to more than 2 weeks before females (Petranka 1998a). Adults in northern populations tend to breed earlier than those in southern populations (Petranka 1998a). Klemens (1993) documented peak breeding in Connecticut from mid-September to early October. Males tend to leave the ponds in early October, while females remain in ponds for several weeks to brood eggs. Females generally do not leave ponds until late October or early November in Rhode Island (Paton and Crouch In press).

Metamorphs emigrate from breeding pond between mid-June and mid-July (Paton and Crouch In press).

 

 
REPRODUCTION
Marbled salamanders are one of only two Ambystoma salamanders that mate and oviposits their eggs on land, all other species use aquatic breeding sites (Petranka 1998a). Marbled salamanders migrate to dried-up pond basins during August in Rhode Island, with males generally preceding females. Once females arrive, males initiate courtship by quickly moving around, bumping into females (and males), and lifting them near the tail and cloacal region (Petranka 1998a). After a protracted dance, a male and female pair moves around in circles, while keeping their cloacal regions in contact. Males eventually deposit a spermatophore on the ground. A female positions her cloaca over the sperm cap and picks up seminal fluid from the top of the spermatophore (Petranka 1998a).
 
EGG MASS
Eggs are oviposited singly in small depressions usually beneath a sheltering object such as logs, bark, leaf mold, or other debris (Green and Pauley 1987). An average clutch size consists of approximately 100 eggs with a large range from 50 to 232 (DeGraaf and Yamasaki 2001). Having deposited the eggs, the females coil around the clutch and broods it. Females remain with the eggs until hatching, which may take one-half month to several months. Eggs will not hatch until inundated with water, so the brooding period is a function of the chronology of pond filling (Petranka 1998a).

According to Jackson et al. (1989), females tend to select oviposition sites with high vegetative cover and tend to concentrate in the lower portions of pond basins in South Carolina. Nest success was highest for nests in deepest parts of the basin, where nests were located randomly. In contrast, nests at mid to high elevations were non-randomly aggregated.
 
LARVAE

Typically, eggs hatch in early November as ponds refill and eggs are flooded. The larvae then overwinter in ponds, although they do not grow much. As pond temperatures warm in the spring and invertebrates become more available, metamorphosis takes place much more rapidly. A. opacum near metamorphosis in late April and early May when the larvae of spring breeding species such as A. maculatum hatch. (Klemens 1993). Larvae are aquatic and primarily nocturnal (DeGraaf and Yamasaki 2001). As pond temperatures warm in the spring and invertebrates become more available, metamorphosis takes places much more rapidly. In New Jersey, the larval period is 135 days (Hassinger et al. 1970).

Hatchlings and small larvae tend to congregate in leaf litter in warm, shallow water during the day. We have been relatively successful dip netting for larvae in the middle of the day at pond edges (Paton and Egan 2001). At night, they disperse more evenly throughout the ponds and feed in the water column (Petranka 1998a). Occasionally, recently transformed individuals can be found beneath litter and debris around the margins of breeding ponds, but typically, metamorphs disperse from ponds during rainy weather soon after transforming (Petranka 1998a).


Marbled salamander larva


 
METAMORPHS

In Rhode Island, peak emigration of metamorphs takes place from about mid-June through 1 July, with metamorphs leaving the pond as late as late July (Paton and Crouch In press). This is slightly later than reported by Petranka (1998a) who suggested that metamorphosis occurs primarily in May and June in central and northern areas of the range, and in March and April in the south. The length of larval period varies depending on climatic patterns and the time of hatching (Petranka 1998a).

A note of caution to biologists working in ponds in Rhode Island. Not all larval salamanders seen in early spring (e.g., January-March) are A. opacum, as occasionally A. maculatum will overwinter in vernal ponds in Rhode Island (Whitford and Vinegar; S. Egan, unpubl. data).


 
JUVENILES
Recently transformed juveniles are brown or black with light flecks, and the flecks become more pronounced and form lichen-like patterns within 1-3 weeks after metamorphosis (Petranka 1998a). Klemens (1993) felt newly transformed and young salamanders are suffused with a purplish gray pattern, which later coalesces into crossbands. Juveniles begin developing the adult pattern within 1-2 months after transformation (Bishop 1941)

Sexual maturity: 15-18 months (Degraaf and Yamasaki 2001).
 
FOOD
Adults
Adult feed on Arthropods, including adults and larval insects, and crustaceans. They also take earthworms and mollusks (DeGraaf and Yamasaki 2001). Bishop (1941) reported that adults ate earthworms, snails, slugs, staphylinid beetles, ants, orthoptera, and diptera and that larvae ate small crustaceans and snails.
Larvae
Larvae eat small aquatic insects, crustaceans, and other small invertebrates, and are cannibalistic. In addition, once wood frog eggs hatch, they readily feed on larvae wood frogs and spotted salamanders (Klemens 1993), which increases their growth rate dramatically. During that short period that both species share the pond, the larger A. opacum larvae exploit different invertebrate food resources than the minute A. maculatum.
 
PREDATION
Adults
{Predation Adults}
Larvae
{Predation Larvae/Tadpoles}
 
CONSERVATION CONCERNS

Marbled salamanders are listed as a threatened species in Massachusetts, and Lazell (1979) attributed their drastic declines in Massachusetts to a combination of factors including pollution, habitat fragmentation, and acid rain. However, Klemens (1993) mentioned that Massachusetts is the northern limits of their range, and declines in the region may be due a to range retraction. In the southeastern United States, the greatest environmental threat to this species is loss of bottomland hardwoods and associated vernal pool habitats (Petranka 1998a). Thousands of local populations of marbled salamanders have already been eliminated by habitat loss, and more will be lost in the future. In New England, urban sprawl has eliminated marbled salamanders from large portions of their range on western Long Island and lower Westchester County, and they probably will become scarcer on eastern Long Island and in the Hudson Valley as urbanization continues (Klemens 1993).

Pechman et al. (1991) found that marbled salamander populations act as metapopulations, therefore some contact between sites must be maintained for population persistence. Isolation of populations is invariably the precursor of extirpation. Taylor and Scott (1997) summarized existing demographic data for marbled salamanders and suggested that at least 70% adult survivorship, or an immigration event from adjacent populations, was necessary for population persistence. High adult survivorship is necessary because recruitment is so sporadic

In Rhode Island, marbled salamander populations appear to be relatively secure, at least for the short term (Klemens 1993). However, if suburbanization of the western sections of the state continues, populations could easily be extirpated. Raithel (unpubl. data) observed high rates of adult and juvenile mortality caused by auto traffic, which must negatively affect populations. Other factors affecting marbled salamanders, including increased environmental acidity and pollution, may impact populations (Lazell 1979), but habitat loss and fragmentation is probably the greatest threat to marbled salamanders in Rhode Island. At the Alton Jones campus, the marbled salamander population remains relatively stable at one breeding pond in a relatively unfragmented, mixed deciduous/coniferous forest over 1000 acres in size (T. Doty and B. Shoop, pers. comm.). This same area has been aerial sprayed twice with Carbaryl (Sevin) (Doty 1978), often gets fairly acidic rainfall, and has had outbreaks of the bacteria Aeromonas hydrophila, which can negatively impact wood frog productivity (Nyman 1985).

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