Amphibians of North Carolina
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NC Records

Siren lacertina - Greater Siren

Taxonomy
Class: Amphibia Order: Caudata Family: Sirenidae
Taxonomic Comments: Villela and Brandon (1992) reported that museum specimens from northern Mexico and southern Texas that were previously identified as Siren intermedia more closely fit the description of S. lacertina. The authors tentatively identified these specimens as S. lacertina based primarily on their size. Recent studies suggest that the taxonomic status of populations that were previously referred to as either S. intermedia or S. lacertina may contain undescribed species. One occurs in south Texas (LaFortune 2015), and perhaps others occur along the Gulf Coast (Graham et al. 2018).
Species Comments: This is one of the largest salamanders in North America, being rivaled only by Cryptobranchus and Amphiuma (Petranka 1998). It is the largest salamander in North America based on weight and the third largest based on length.
Identification
Description: The Greater Siren is a very large, eel-shaped salamander that lacks hind limbs. It has greatly reduced front limbs that each have four toes and a shovel-like head that is used for burrowing in pond and stream bottoms (Beane et al. 2010, Petranka 1998). The adults vary from 50-98 cm TL, but most are < 70 cm. Individuals have bushy external gills just in front of the front limbs that are retained for life. The terminal two-thirds of the tail is finned, and the ventral fin is narrower than the dorsal fin. The modal number of costal grooves between the front limbs and the cloaca is 37-38. The ground color of the dorsum of older juveniles and adults varies from olive green to light grayish and is often overlain with numerous irregular dark spots on the head, back, and sides. The sides of the body are lighter colored than the back and are sometimes colored with inconspicuous flecks or blotches of pale green. The bluish gray venter is often flecked with pale green coloration. Males have enlarged masseter muscles which often make the head of older males appear larger than that of females of similar size.

The hatchlings are the pond type and have prominent dorsal and caudal fins, a pale gray dorsum, and a stripe from the gills to the base of the tail. Young juveniles have cornified toe tips that resemble claws, a prominent light yellow or reddish stripe down each side of the body, and (in some populations) a narrower, less prominent ventrolateral light stripe. Striping on the body is reduced or is lost during the first year of life as the juveniles transition towards the adult coloration and patterning (Petranka 1998). Many become uniformly dark gray with varying amounts of mottling on the tail fin.

Siren lacertina often coexists locally with the Lesser Siren (S. intermedia). The two are easily confused since the size ranges overlap. The latter lacks pale green flecking on the sides and belly and has a modal number of only 32-33 costal grooves, compared to 37-38 in S. lacertina.
Vocalizations: The Greater Siren makes clicking or yelping noises similar to those of S. intermedia that may function in intraspecific communication (Carr 1940, Gehlbach and Walker 1970). The exact function of these noises is poorly resolved.
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AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Greater Siren is found primarily in Coastal Plain wetlands from the vicinity of Washington, D.C. southward to southern Florida and westward to southwestern Alabama. In many areas in the northern and western portions of its range S. lacertina is uncommon and occurs in scattered populations. Local populations appear to reach their highest densities in Florida, southeastern Georgia, and eastern South Carolina where the species is often abundant (Petranka 1998). Scattered populations have been found in North Carolina throughout much of the Coastal Plain, as well as in Wake County in the eastern Piedmont.
Distribution Reference: Beane et al. (2010); Petranka (1998)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: Siren lacertina is most commonly found in permanent or semipermanent aquatic habitats that have dense aquatic vegetation and soft substrates such as organic muck that allows burrowing. Much like the Two-toed Amphiuma and the Lesser Siren, it can be found in swamps, farm ponds, vegetated shallows in lakes, abandoned rice fields, slow-moving streams, flooded ditches, seasonal wetlands and other still and sluggish waters (Beane et al. 2010, Petranka 1998). Schalk et al. (2010) found that summer-active animals at a South Carolina site were most commonly trapped in relatively deep water that had floating and emergent vegetation and relatively high densities of aquatic insects, while Sorensen (2003) only collected animals at her study sites in Florida and southern Georgia in vegetation mats. Snodgrass et al. (1999) surveyed sites in South Carolina for A. means, Siren intermedia, and S. lacertina and found that the likelihood of finding these large aquatic species increased with the seasonal duration of the sites and whether other sites were in close proximity. Sites that held water for less than six months were not occupied, and those that were relatively close to adjoining wetlands were more likely to have populations of Siren lacertina.
Biotic Relationships: This species is preyed upon by a variety of aquatic predators such as snakes, the Great Blue Heron and other wading birds, and other large predators. American alligators are important predators. In a Florida study 35 S. lacertina were found in a sample of 350 alligators (Delany and Abercrombie 1986).
See also Habitat Account for Coastal Plain Still and Sluggish Waters
Life History and Autecology
Breeding and Courtship: The courtship behavior has never been documented, but fertilization is thought to be external since the females lack spermathecae and the males lack cloacal glands (Petranka 1998). Ultsch (1973) found that eggs that are laid by captive females that were isolated from males did not develop. This suggests that females are incapable of storing sperm internally and that the males fertilize the eggs as they are laid. The mystery behind Siren courtship and fertilization appears to have been solved by Reinhard et al. (2014) who observed courtship and parental care in captive Siren intermedia, which is a close relative. A male that was observed and filmed actively constructed a nest with aquatic plants and courted a female inside his shelter. After the female deposited an egg, the male fertilized it externally. The male cared for the clutch and even guarded the hatchlings for a brief period (details of courtship and parental care are under the account of S. intermedia). Based on these observations, it is very likely that S. lacertina also engages in external fertilization.

Breeding appears to occur from January through March (Luhring 2008, Petranka 1998). Hanlin and Mount (1978) found that males produce spermatozoa and females have ovarian eggs that reach their maximum size in February and March in a south Alabama pond. The sex ratio of 42 males and females that they collected did not differ significantly from 1:1. Luhring (2008) found that bite marks were observed on nearly all of the reproductive adults at a South Carolina site during the breeding season (especially during February), but were not evident during the rest of the year.
Reproductive Mode: Females in Alabama, Florida, and South Carolina populations appear to primarily oviposit in February and March. Eggs have almost never been found in nature, and little information is available on nest site selection. Goin (1947) found five eggs on 4 February in a shallow ditch in northern Florida that were in a bed of aquatic plants, while a large, grape-like cluster of eggs near hatching was found in early May while dredging water hyacinths in Florida (Petranka 1998). Most other records are based on captive females that laid eggs shortly after being placed in aquaria. Two females that were collected by Luhring (2008) in South Carolina laid eggs on 14 February and 12 March after being held for a brief period in captivity. A female from Florida laid eggs between 16-21 February (Noble and Richards 1932), while other Florida females collected on 4-6 February laid eggs within 3 days after capture (Ultsch 1973). The eggs were attached singly or in small groups of < 10 eggs to the substrate by their outer, adhesive egg capsules and lacked stalks.

The freshly laid eggs are dark brown above, average 4 mm in diameter, and are surrounded by three jelly envelopes (Hanlin and Mount 1978, Noble and Marshall 1932, Salthe 1963). This species is one of the most fecund salamanders in North America. One specimen collected by Hanlin and Mount (1978) contained about 1,400 enlarged ovarian eggs, although small adults appear to lay far fewer eggs. The young of the year first appear in late April and early May which suggests an incubation period of about 2 months (Ultsch 1973).
Aquatic Life History: The juveniles often hide in thick aquatic vegetation during the day and are most active in the water column at night where they feed on small invertebrates (Petranka 1998). At one site in Florida the adults were found in water 76-91 cm deep, while juveniles utilized shallower water that was only 15-30 cm deep (Duellman and Schwartz 1958). The young larvae grow relatively rapidly for the first two years of life. Young of the year in Florida can grow to 75 mm SVL by mid-October (Ultsch 1973). Those in a South Carolina population reached an average SVL of about 100 mm during their first year and around 200 mm during their second year (Luhring 2008). They were estimated to reach sexually mature during their fourth year.

The adults are active at night and frequently hide in burrows during the day. At one Florida site, individuals lived in a canal bank in burrows that slanted downward before leveling off into enlarged chambers that were 15 cm in diameter (Duellman and Schwartz 1958). The larger juveniles and adults consume a wide variety of prey, but sometimes feed rather heavily on molluscs (Moler 1994, Petranka 1998). Dietary records include filamentous algae and a large number of snails in a Virginia specimen (Burch and Wood 1955), and snails, insects, crayfish, and a fish in Florida specimens (Duellman and Schwartz 1958, Hamilton 1950). Gut items in Alabama specimens included mud and bottom debris, filamentous algae, crayfishes, spiders, snails, clams, and representatives of several orders of insects (Hanlin 1978). The insects included odonates, beetles, dipterans, and several other taxa.

The presence of filamentous algae and other plant material in the guts of sirens have caused many to speculate as to whether S. lacertina derives energy from plant material. Recent studies suggest this may be the case. The Greater Siren has a complex chewing mechanism that may allow it to crush and process plant material before swallowing. It also is known to intentionally eat algae, has a complex gut that could support plant-digesting microbes, and shows evidence of fermentation occurring in the gut (Hill et al. 2015, Pryor et al. 2006, Schwartz et al. 2021). It might best be treated as a facultative herbivore.

Individuals show both diel and seasonal patterns of activity. Adults in an Alabama population were most active 2 hours after dark and 2 hours before dawn (Hanlin and Mount 1978). A seasonal peak in feeding activity occurred during June and July, while a seasonal low in activity occurred from October through December. Luhring (2008) found a seasonal peak in January and June in a South Carolina population.

The Greater Siren often inhabits semipermanent ponds or shallow lakes that can dry or undergo major contractions during droughts. Trapped individuals survive by aestivating in underground burrows without food and can survive for long periods of time (Carr 1940, Freeman 1958, Hanlin and Mount 1978). Aestivating individuals survive in cocoons of sorts that are composed of sloughed skin cells and often rest in an S-shaped configuration with the body in contact with the soil (Etheridge 1990a, Petranka 1998). This posturing allows water exchange with the soil and minimizes the probability of desiccating. Waller (2009) noted that 278 aestivating animals were found in the bottom muck of Lake Okeechobee during a drought when bulldozers scraped muck from the lake bottom during a restoration project.

When food is abundant, individuals develop large fat reserves in their tails that allow them to endure prolonged periods without food (Martof 1969). One siren that was maintained without food died 26 months later after losing 45% of its initial body weight, while a second died after 5.2 years after loosing 86% of its initial weight. Etheridge (1990b) found that resting metabolic rates are 60-70% lower in aestivating animals compared to active animals, which helps to conserve energy reserves. Data on survival and longevity in nature are not available, but adults have been kept in captivity for as long as 25 years (Nigrelli 1954).


General Ecology
Population Ecology: Factors that regulate local populations are poorly resolved. Local populations can reach high densities and territoriality as seen in S. intermedia (Reinhard et al. 2014) could limit adult population sizes. Bite marks that are associated with the breeding season suggest that males may compete for females. Sorensen (2003, 2004) estimated an average of 1.3 salamanders/m2 of lake bottom at a Florida site and a biomass of 233 g/m2. Luhring (2008) reported an estimated density of 0.005 sirens/m2 at a South Carolina site.
Community Ecology: The Two-toed Amphiuma and the Greater Siren (Siren lacertina) commonly co-occur in coastal wetlands throughout the southeast and could potentially compete or function as mutual predators on each other's young (Snodgrass et al. 1999). Schalk et al. (2010) examined summer habitat use in a South Carolina pond and found evidence of partial spatial segregation. Siren lacertina was mostly found in relatively deep areas of the pond where aquatic insects were most abundant and floating and emergent vegetation prevailed, while A. means occurred more frequently in relatively shallow areas where fish and crayfish were most abundant and floating and submerged vegetation prevailed. Additionally, S. lacertina appeared to use the entire water column, while A. means were only caught in the lower water column.
Adverse Environmental Impacts
Habitat Loss: The construction of reservoirs, canals, farm ponds and other human features on the landscape has likely benefitted this species, particularly where vegetated shallows are present. At the same time, countless natural wetlands have been destroyed or degraded in the Southeast since European settlement.

Snodgrass et al. (1999) surveyed intermittent ponds in South Carolina and provided data which suggest that prolonged droughts may cause local populations to be extirpated. This species has a difficult time dispersing over land or in very shallow water (Schalk and Luhring 2010). To disperse to and recolonize isolated wetlands, sirens likely rely on the formation of aquatic connections during flooding events. Flood control programs and road construction can reduce the frequency of local flooding events and reduce watershed connectivity. Connectivity between ponds during flood events is important for maintaining viable metapopulations of this and other aquatic salamanders that cannot readily disperse across land. The outright destruction of wetlands across a landscape also increases the distance to nearest neighbors and likely reduces the probability that local ponds could be recolonized following local extirpations.


Status in North Carolina
NHP State Rank: S3
Global Rank: G5
Status in North Carolina: W3

Photo Gallery for Siren lacertina - Greater Siren

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Recorded by: Brian Bockhahn
United States Co.
Comment: 38 Costal grooves counted. Caught in aquatic traps by NCSU doing waterdog surveys.		Recorded by: Brian Bockhahn
United States Co.
Recorded by: Brian Bockhahn
United States Co.