Black-spotted newt, Southern newt, Texas Black Striped Newt
© 2011 Timothy Burkhardt (1 of 5)
Notophthalmus meridionalis (Cope, 1880)
Kelly J. Irwin1
1. Historical versus Current Distribution. Black-spotted newts (Notophthalmus meridionalis) range from northern Veracruz, Mexico, north to southern Texas (Mecham, 1968a). Two subspecies of black-spotted newts are currently recognized: Texas black-spotted newts (N. m. meridionalis) and Mexican black-spotted newts (N. m. kallerti). Only Texas black-spotted newts occur in the United States.
In Texas, black-spotted newts inhabit the Coastal Plain of the Tamaulipan Biotic Province, but in Mexico they have been recorded at elevations of 610 and 800 m (Mecham, 1968a). Bishop (1943) mapped the distribution of black-spotted newts from as far north as Waco, Texas (Strecker, 1908c), and as far east as Houston, Texas (Harwood, 1930, 1932). Dixon (2000) provides the most current and accurate distribution map for the species. Black-spotted newts have been recorded from all Texas counties bordering the Gulf Coast, south from Aransas and Refugio counties, and the central portion of the Tamaulipan Province, south from Bexar County. Strecker (1908c, 1922) reported black-spotted newts from Bexar, Falls, and McClennan counties, but these records are now considered questionable or erroneous (B.C. Brown, 1950; Raun and Gehlbach, 1972). Brown (B.C., 1950) suggested that the locality record for Bexar County was labeled as coming from the shipping point rather than the actual collection locality. However, Dixon (2000) mapped the Bexar County record at the northern terminus of the Tamaulipan Biotic Province. The Falls and McClennan County records are undoubtedly erroneous, for they are about 200 km northeast of the Bexar County record and most certainly represent observations of eastern newts (Notophthalmus viridescens). While Strecker (1908b) listed black-spotted newts from Victoria County, both Mecham (1968a) and Dixon (2000) suggest that this record may represent specimens of eastern newts. Dixon (2000) states that the Duval County record was unverified, however a record from McMullen County (Taggart, 1997b) filled the gap between the Bexar and Duval County records, thereby lending credence to earlier records. Taggart (1997b) provided U.S. National Museum (U.S.N.M.) numbers for specimens from both counties, but did not verify specimen identifications. Boundy (1994b) reported a record from Starr County, substantiating an unverified report of black-spotted newts in Starr County (Irwin, 1993).
2. Historical versus Current Abundance. Oliver et al. (1980) reported 28 black-spotted newts found beneath fallen (palm?) logs in a marshy clearing on 24 January 1964, at Southmost Ranch, south of Brownsville, Cameron County, Texas. Judd (1985) captured 17 individuals at Laguna Atascosa National Wildlife Refuge, Cameron County, Texas, in March 1983. These newts were seined from an earthen pond on the margin of an old field. Judd (1985) also reported the discovery of three black-spotted newts from an old corral under logs on the outskirts of Brownsville, Cameron County, Texas, on a misty rainy day in January 1983. Rappole and Klicka (1991) recorded seining 32 newts from a temporary pond on Laguna Atascosa National Wildlife Refuge, Cameron County, Texas, on 25 August 1987. Based on their sample size and pond size, they estimated a population of 533 black-spotted newts and 250 Siren sp. (see Siren texana account, this volume) at this locality. On the same date, they sampled a pond in northern Tamaulipas, Mexico, estimating a total of 140 Notophthalmus and 280 Siren at this site. In mid February 1988, Rappole and Klicka (1991) found 14 newts of various age classes under debris in a junk yard near Vattmannville, Kleberg County, Texas. By digging with a shovel, four more newts were unearthed at this same locality on 29 February 1988.
3. Life History Features. Mecham (1968a) noted that descriptions of the eggs, early development, and mating behavior are lacking for this species. Indeed, most aspects of the natural history of black-spotted newts are undocumented (Petranka, 1998).
A. Breeding. Reproduction is aquatic. Mecham (1968a) clarified the description of breeding habits reported by Strecker (1922) as the misidentification of eastern newts (Bishop, 1943; Petranka, 1998). Mecham (1968a,b) reports that mating is tied to rainfall and can occur at any time of year. Rappole and Klicka (1991) provide the following observations on reproduction. Courtship was said to occur throughout the year in captive black-spotted newts, but no specific dates were provided. Courtship was described as similar to that of eastern newts. Females were observed swimming and hovering over deposited spermatophores, but were not observed to grasp spermatophores with the hind feet as reported in eastern newts. Because captive newts do not feed at temperatures below 10 ˚C, and little active aquatic life is found in breeding ponds in January and February, Rappole and Klicka (1991) suggest that there is no breeding activity in southern Texas from December–February; they did find reproductive activity among aquatic adults in March and August.
i. Breeding migrations. No true breeding migrations have been reported for this species (but see "Seasonal Migrations" below).
ii. Breeding habitat. Mecham (1968a) lists permanent and temporary ponds, roadside ditches, and pools of small streams as habitat for adults, juveniles, and larvae. In Texas, black-spotted newts were found to breed in shallow ephemeral ponds ranging in depth from 0.5–2 m, with firm clay bottoms, and some with rooted macrophytes. Ponds that contained newts had salinities ranging from 0.5–1.0‰. Newts were also found in dried wetland ditches along railroad rights-of-way, which suggests that adults breed in these ditches when they fill with rain water. Newts were not found in water bodies with predatory fish, high salinity, intense cattle usage, or those with agricultural runoff (Rappole and Klicka, 1991).
B. Eggs. The following information is based on the observations of Rappole and Klicka (1991). Eggs are laid singly, requiring about 3 min to be laid, at intervals of 6–30 min. As an egg was laid it was pinched off, by compressing the cloaca against the hind feet, with soles facing each other. This process was done as the hind feet grasped submerged vegetation and the egg was effectively glued to the surface of the vegetation. Eggs were also laid on other surfaces or in the water column. The female parent or other newts often ate free-floating, unattached eggs. Ova are blue-green in color. Larvae emerged from eggs in 12–14 d.
i. Egg deposition sites. Eggs are attached to submergent vegetation.
ii. Clutch size. Rappole and Klicka (1991) did not provide any data on the total number of eggs laid by a single female. References to this species laying 300 eggs should be ascribed to eastern newts until confirmed reports are available.
i. Length of larval stage. Rappole and Klicka (1991) did not report the duration of the larval stage in captive specimens. Larvae were described as being similar to those of eastern newts—aquatic with external gills, smooth skin, green pigmentation, and a laterally compressed tail.
ii. Larval requirements. Unknown.
a. Food. Unknown, but larvae are presumably carnivorous as are other members of the genus.
b. Cover. Unknown.
iii. Larval polymorphisms. Unknown and unlikely.
iv. Features of metamorphosis. Additional research is needed, for example to clarify the existence and duration of a true eft stage in this species. Black-spotted newts are considered by some authors to lack a well-defined, dispersive or migratory eft stage (Mecham, 1968a; Petranka, 1998). Based on his seining of newly metamorphosed young and subadults in association with sexually mature adults, Mecham (1968b) raised doubts that a true terrestrial eft stage occurs in black-spotted newts. Conversely, Rappole and Klicka (1991) state that upon metamorphosis the larvae transform into a terrestrial or “eft” stage with cornified skin and round tail, in cross section. Based on research on eastern newts (Gill, 1978; Harris, 1987a), Rappole and Klicka (1991) suggest that both neotenic and eft stages could occur in black-spotted newts. Further, these authors state that the duration of the eft stage could be dependent upon the availability of aquatic breeding sites. They also state that metamorphosis from eft to breeding adult is rapid. Captive terrestrial forms developed first signs of a keel on the tail within 2 d of being placed in an aquarium, and developed fully aquatic, breeding adult characteristics within 2 wk (Rappole and Klicka, 1991). As in other members of the genus, males develop a heavily keeled tail, horny black breeding excrescences on the hind legs, and a distinctly triangular-shaped head with puffy folds of skin. Terrestrial individuals with cloacal swellings contained undeveloped eggs in the ovaries. Rappole and Klicka (1991) propose that it might be possible to sex non-reproductive newts based on head and tail size and shape. These observations suggest that adults revert from a terrestrial phenotype to a breeding aquatic phenotype when conditions are favorable, as is seen in the eastern newts and striped newts (N. perstriatus), the two other members of this genus.
v. Post-metamorphic migrations. Unknown. Mecham (1968b) found juveniles and adults under rocks near a recently dried pond in Tamaulipas, Mexico, suggesting that these animals do not disperse great distances from breeding sites.
vi. Neoteny. Mecham (1968b) collected a reproductively mature female with gill rudiments, suggesting neoteny.
D. Juvenile Habitat. Mecham (1968b) suggests juveniles may remain aquatic until reproductively mature, unless their pond dries or high temperatures cause them to seek cover on land.
E. Adult Habitat. In Texas, the presence of black-spotted newts appears to be related to soil type. Deep, poorly drained, clayey sediments (such as the “Tiocano” and “Edroy” clay soils) with slow permeability allow for the formation of ephemeral ponds or wetlands during periods of heavy rain. Most adults have generally been found in the vicinity of, or in, such breeding ponds (Mecham, 1986b; Rappole and Klicka, 1991). Several localities were seasonally dry ditches along railroad rights-of-way or highway borrow pits (Rappole and Klicka, 1991). The presence of intact Tamaulipan thorn forest in clayey soils, with ephemeral wetlands, should be considered optimal adult habitat. With the advent of extensive land clearing for row crop agriculture and root-plowing of native brush for cattle grazing, much of the black-spotted newt’s original habitat has been lost. For example, Rappole and Klicka (1991) described a locality as swampy pasture with shrubs and grasses, black loam soil over clay, and two livestock ponds. Many individuals had been found at this site, which was subsequently root plowed, effectively destroying the surrounding terrestrial habitat used by adults and subadults. In addition, Rappole and Klicka (1991) identified several sites in Cameron, Kleberg, and Kenedy counties in Texas that they considered to be metapopulation centers.
F. Home Range Size. Unknown. Mecham (1968a,b) found juveniles and adults under rocks near a recently dried pond, indicating that these animals do not migrate to more suitable, but distant, habitats. Based on several observations (see "Seasonal Migrations" below), newts may disperse greater distances from breeding sites than current information suggests.
G. Territories. Unknown, but has not been observed in this family.
H. Aestivation/Avoiding Dessication. Black-spotted newts inhabit a region prone to periodic droughts and extreme temperatures. Mecham’s (1968a,b) observations indicate that animals under these conditions will seek shelter under cover objects in and near dried breeding sites. Further, Rappole and Klicka (1991) provide evidence of burrowing and use of existing burrows, which may be used to aestivate. In February 1988, four newts were unearthed by digging at a site that had previously produced newts by turning of ground cover in Kleberg County, Texas. In March 1988, these authors dug up a live newt 15 cm below the soil surface along the margins of a known breeding pond in Cameron County, Texas. In the field, newts were found in fissures of dried soil along a drift fence. Newts may also use crab burrows as retreats. Captives utilized crayfish burrows and manmade burrows; they were also observed to burrow in the soil at or below the soil/water interface.
I. Seasonal Migrations. No documented seasonal migrations have been reported. However, Thornton (1977) found one individual crossing a gravel road at night in Cameron County, Texas, and L. Laack (personal observation) found several newts crossing a road on a rainy night at Laguna Atascosa National Wildlife Refuge, Cameron County, Texas. Taggart (1997b) captured an adult male crossing a paved highway on a rainy night in McClennan County, Texas, at 2140 hr on 31 August 1995. Based on these limited observations, adult migrations to or from breeding sites and dispersal of juveniles are probably made on nights with high humidity or rain.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Judd (1985) recorded the presence of adult Siren sp. and Rio Grande leopard frog (Rana berlandieri) tadpoles in the same pond as black-spotted newts in Cameron County, Texas. Rappole and Klicka (1991) made several observations of interspecific associations. While searching under railroad ties in January 1988, a newt and a four-lined skink (Eumeces tetragrammus) were found in close proximity in Kenedy County, Texas. In early March 1988, a newt was found under railroad ties in a ditch lined with willows in Kleberg County, Texas, where they had previously found a Great Plains narrow-mouthed toad (Gastrophryne olivacea) and an individual siren (again, see account in this volume for a discussion of the confusion surrounding the identification of south Texas sirens) in late February 1988. Rappole and Klicka (1991) also list barred tiger salamanders (Ambystoma tigrinum mavortium) as an associate species in newt breeding ponds, but provide no further details.
The following sympatric species were found on the Audubon Sabal Palm Grove Sanctuary, Cameron County, Texas: Rio Grande chirping frogs (Eleutherodactylus cystignathoides), Coastal-Plain toads (Bufo nebulifer), Rio Grande leopard frogs, Mexican treefrogs (Smilisca baudinii), four-lined skinks (Eumeces tetragrammus), Texas spotted whiptail lizards (Cnemidophorus gularis), Texas spiny lizards (Sceloporus olivaceus), green anoles (Anolis carolinensis), black-striped snakes (Coniophanes imperialis), Texas indigo snakes (Drymarchon corais), speckled racers (Drymobius margaritiferus), racers (Coluber constrictor), rough green snakes (Opheodrys aestivus), and Texas coral snakes (Micrurus tener; K.J.I., personal observations).
L. Age/Size at Reproductive Maturity. Unknown.
M. Longevity. Unknown.
N. Feeding Behavior. Rappole and Klicka (1991) provide the most extensive information on food and feeding behavior of black-spotted newts. They compared the natural prey items of striped newts, as compiled by Christman and Franz (1973), to prey taxa recorded in black-striped newt ponds, and found similarity between species of recorded prey taxa with those present in black-spotted newt breeding ponds. Stomach contents of wild-caught black-striped newts contained seed shrimp (Ostracoda), small snails (Gastropoda), and unidentified insect larvae and eggs. Although they do not provide any data showing percent composition of diet, they state that ostracods were the primary prey of wild caught individuals. Captive newts readily consumed fairy shrimp (Anostraca), scuds (Amphipoda), odonate larvae (Insecta), eggs of conspecifics, and chunks of flesh of mammals and birds.
Rappole and Klicka (1991) describe two types of feeding behavior in captive specimens: a sit-and-wait approach and stalking. When sitting and waiting, a newt lies motionless, and when a potential prey item was detected, it would coil and arch its back, sometimes holding this position for several seconds. Then with extreme rapidity, the newt suddenly uncoils in a snapping motion and attempts to engulf the prey item. When stalking, newts were observed to follow amphipods and then suddenly grab them. During daylight hours, captive newts would remain hidden under terrestrial debris, then forage at night. They observed that captive newts became sluggish at < 10 ˚C and did not feed at cooler temperatures.
O. Predators. Rappole and Klicka (1991) found no direct evidence of predation on black-spotted newts, but suggested that turtles or sirens might be possible aquatic predators. They found several newts at one locality that had scars or “bite marks” on the abdomen, neck, and head. Sirens were syntopic at this locality, and as a test, one was placed in an aquarium with a newt. The newt and siren co-existed in the aquarium for 1 wk without any signs of visible interaction. An examination of field-caught siren feces revealed the presence of ostracods, odonates, and snails, but no newt remains.
P. Anti-Predator Mechanisms. As with other members of the genus Notophthalmus, black-spotted newts secrete skin toxins that deter or repel potential predators. Investigators found that a skin irritant was present in the skin when touched to the investigator’s lips (Rappole and Klicka, 1991). Rappole and Klicka (1991) record the first instance of an unken type of posture in the black-spotted newt. When efts were found under debris or in burrows, they would respond to being touched by immediately contracting into an “S” shape and then flipping onto their backs exposing the bright orange-yellow belly, an aposematic color.
Christman (1959), as cited by Rappole and Klicka (1991), reported production of a soft click sound in eastern newts. Captive black-spotted newts were observed to produce a click vocalization, predominately at night. Black-spotted newts also produced a sound described as a squeal when being captured (Rappole and Klicka, 1991).
Q. Diseases. Unknown.
R. Parasites. Unknown. The descriptions of new species of nematodes (Harwood, 1930, 1932) taken from newts in the vicinity of Houston, Texas, were undoubtedly based on specimens of eastern newts.
4. Conservation. The Texas Parks and Wildlife Department currently lists black-spotted newts as Endangered, and specimens are protected from collection. Despite this, and the fact that black-spotted newts occur in the United States only in Texas, these animals have no Federal listing status. Continued land clearing for agriculture and urban development pose the greatest threats to these salamanders. Over 95% of the original Tamaulipan brushland of the lower Rio Grande valley has been destroyed as a result of these activities. In addition, the impacts of exposure to agrichemicals on reproductive success and outright mortality are unknown. The excavation of temporary ponds within existing brushland habitat would create new breeding sites, bolstering maintenance of viable local populations.
1Kelly J. Irwin
2Frank W. Judd
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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