Little is known about the expected lifespan of greater sirens in the wild or captivity. However, a single greater siren residing in the Cincinnati zoo has been reported to be at least 25 years of age.
Range lifespan
Status: captivity: 25 (high) years.
Average lifespan
Status: captivity: 25.0 years.
Average lifespan
Sex: female
Status: captivity: 14.8 years.
Greater sirens have been found in the digestive tracts of American alligators and red-bellied mud snakes. Otherwise, little is known about their predators. To avoid predation, greater sirens employ several techniques. They can produce an array of sounds that can intimidate predators. These include yelps (similar to calls made by green tree frogs), hissing, croaking and a sound similar to that of a young duck. In addition, greater sirens may use their muscular tails to make a hasty getaway. As a last resort, a greater siren can deliver a painful bite to ward off predators.
Known Predators:
Anti-predator Adaptations: cryptic
Greater sirens have a similar overall body shape to other salamanders, but have reduced forelimbs (containing four toes each) and no hind limbs giving, them rather eel-like appearance. Their body is round in cross section and encompasses about two thirds of their total length, with the rest being composed of a long, vertically flattened tail. The head is rounded into a square jaw with one small eye on each side. They possess external gills with three gill appendages a few centimeters behind their eyes, but before their legs. These appendages are crowded in the front of the body as opposed to being spread-out. Their skin is an olive or grayish brown color with black speckles and yellow dashes along its length (particularly on the dorsum). The underbelly tends to be lighter in color than the skin on the sides and back. Greater sirens can reach a length of 97 cm, but average around 62 to 77 cm.
Greater sirens can be distinguished from lesser sirens (Siren intermedia) by counting the number of costal grooves (lateral indentations that run down the length of a salamander's body) present. Greater sirens have 36 to 40 costal grooves as opposed to the 31 to 35 costal grooves found on lesser sirens. Additionally, lesser sirens are uniformly dark, more slender, and have sharper tails. Newly hatched greater sirens are striped and have a yellow or red triangular marking on their snout, while newly hatched lesser sirens lack stripes and snout markings.
Range length: 49 to 97 cm.
Average length: 62 - 77 cm.
Sexual Dimorphism: sexes alike
Other Physical Features: ectothermic ; bilateral symmetry
Because greater sirens are solitary and seldom interact, little information is available regarding modes of intraspecific communication. They are known to produce hissing sounds when threatened by predators, however.
Because the eyes of greater sirens are rather small and they often inhabit areas of high water turbidity or otherwise low visibility, vision is likely to be a secondary sensory modality by which this species perceives its environment. They use an auxilliary olfactory organ (the vomeronasal or Jacobson's organ) to detect prey in these situations. They are also likely to use their lateral line (which most larval amphibians possess and which greater sirens maintain throughout their adult lives) to sense vibrations in their environment. It is thought that they may also be able to sense disturbances in electrical fields using dense arrays of neuromasts that are found on the head.
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical ; electric
Unlike many salamanders, greater sirens lack a terrestrial life stage and are found exclusively in aquatic environments for their entire lifespan. They prefer the shelter of heavily vegetated swamps, ponds, and ditches, but are also found in streams and large lakes. They migrate to shallow water in order to lay their eggs. Hatchlings live among thick vegetation (such as the roots of water hyacinth) and progressively move to deeper water as they mature. Adults spend the majority of their time near the bottoms of pools, entwined in plant roots and branches, or under sunken logs. When bodies of water dry out, greater sirens burrow into the muddy lake or stream bed and enter a state of aestivation to avoid dessication.
Habitat Regions: temperate ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams; coastal
Wetlands: swamp
Greater sirens are found in the southern and eastern United States, along the Atlantic and Gulf coastal plains. They can be found as far north as eastern Virginia and south through the southern tip of Florida, and as far west as southwestern Alabama. There are reports of a disjoint population occupying the Rio Grande valley of southern Texas and northern Mexico. However, further investigation is required to assess the relationship of the two populations.
Biogeographic Regions: nearctic (Native )
Greater sirens are active at night and are primarily carnivorous. However, algae has been found in the digestive tract of some individuals, leading researchers to believe that they may be omnivorous. Greater sirens will prey on insects, crustaceans, gastropods, bivalves, spiders, mollusks, crayfish, and small fish.
Animal Foods: fish; insects; terrestrial non-insect arthropods; mollusks
Plant Foods: algae
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Molluscivore ); herbivore (Algivore)
Greater sirens act as mid-level predators, feeding on insects and other invertebrate species. Greater sirens are also hosts to platyhelminth parasites, including flatworms (Ophiotaenia sireni and Progorgodera foliata) and trematodes (Allassostomoides louisianaensis).
Commensal/Parasitic Species:
Greater sirens benefit humans by keeping aquatic invertebrate and insect populations in check.
Positive Impacts: controls pest population
There are no known adverse effects of greater sirens on humans.
Greater sirens retain larval features throughout life. Their gills remain external throughout their life and they never develop hind limbs. Hatchlings are approximately 11 mm in length and are born with distinct stripes, which gradually fade and are completely lost within the first year of life. Newly hatched individuals will also have a red or yellow triangular marking on their snout. Juveniles tend to be brighter in color and have a more mottled appearance when compared to adult specimens.
Development - Life Cycle: neotenic/paedomorphic; metamorphosis
Greater sirens are considered common throughout the central regions of their geographic range. However, their status throughout the peripheral regions of the range varies between abundant and rare. In Maryland, they are considered endangered. Greater siren populations are difficult to monitor, due to their permanently aquatic lifestyle. Encroachment on habitats by agricultural and urban development, including runoff of harmful pesticides, is the major potential threat to greater siren populations.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Specifics of greater siren mating systems are unknown.
Greater sirens reach reproductive maturity around the age of two to three years. Mating behavior has yet to be observed and reported for this species. However, as in other amphibians, fertilization is assumed to be external. Greater sirens breed once yearly between February and March, although this depends on environmental conditions. Females lay a large clutch of about 500 eggs, which look like small grapes and adhere to each other. The eggs gestate for about two months and hatch in the months of April or May.
Breeding interval: Greater sirens breed once yearly.
Breeding season: Breeding occurs from February to March.
Average number of offspring: 500.
Average time to hatching: 2 months.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
Female greater sirens will guard their eggs in the shallows until they hatch and then return to deeper water. No further parental protection occurs.
Parental Investment: pre-fertilization (Provisioning); pre-hatching/birth (Protecting: Female)
The greater siren (Siren lacertina) is an eel-like amphibian and one of the three members of the genus Siren. The largest of the sirens and one of the largest amphibians in North America, the greater siren resides in the coastal plains of the southeastern United States.
The Greater Siren is the third longest salamander in the western hemisphere.[3] S. lacertina is paedomorphic, as are all sirens. They lack hindlimbs as well as a pelvic girdle, and have external gills all throughout their lives along with small lungs. They lack eyelids, and have an unfused pectoral girdle.[4] Greater sirens measure around 1.5 cm (0.59 in) in length upon hatching and then grow to lengths ranging from 18 to 97 cm (7 to 38 in).[5][6][7] Weight can range from 55 to 1,000 g (1.9 to 35.3 oz).[8][9] Coloration varies throughout their range, but they are generally an olive or gray color with small yellow or green dots on their sides. They have about 36 to 40 costal grooves between their armpits and their cloaca.[10] Younger sirens also have a light stripe along their sides, which fades with age. The front legs, each with four toes, are so small that they can be hidden in the gills.
In terms of sensory organs, greater sirens rely on both a modified Jacobson's organ and a lateral line system over their small eyes. It is possible that they are capable of sensing disturbances in electrical fields.[11]
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Greater siren skull & hyoid
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Greater siren skeleton
Greater sirens are carnivorous and prey upon invertebrates (such as insects, crustaceans, gastropods, bivalves, spiders, molluscs, and crayfish)[12] and aquatic vertebrates (such as small fish)[12] with a possible preference for molluscs,[10] although they have been observed to eat vegetation such as algae.[13][12] In addition, materials that are non-animal were found in their digestive tract added to amounts of 75% or greater. [14] Greater sirens play a crucial role in aquatic food webs and have been described as midlevel predators.[15] Sirens swallow molluscs whole and will pass the shell as waste.[16] They are nocturnal and spend the day in dense vegetation.[11] Their lifespan in the wild is unknown, but in captivity they can live up to 25 years. Greater sirens can vocalize, producing clicks or yelps sounding similar to the call of the American green tree frog.[10] They are predominately found in the deep benthic zone where aquatic insects are most abundant.[17] They are able to aestivate for multiple years if necessary, burrowing into mud and exuding a cocoon of dead skin cells. This has been seen during times of drought and hydroperiod fluctuations.[18] The record can be up to 3 years.[19] Known predators include the American alligator and the mud snake.[11] Other predators of this species are poorly documented. However, on June 19,2008 a greater siren was consumed by a Two-Toed Amphiuma (Amphiuma m.) indicating that this species could be an additional predator of the greater siren.[20]
Their spermatozoa possess a pair of flagella, and their courtship behavior is unknown.[4] Mating occurs in February and March, with mothers guarding clutches of eggs that hatch about two months later. Youth live in shallower water than adults, often among the roots of water hyacinths.[11]
They inhabit the coastal plain from Washington, D.C., to Florida and Alabama.[21] A population of sirens in the Rio Grande has been tentatively determined to be S. lacertina. Greater sirens live in wetlands, preferring those with a slow or nonexistent current and a thick layer of organic material. They are capable of inhabiting seasonal and permanent wetlands given their ability to aestivate,[10] and will burrow into mud if their wetland dries up.[21] Associated habitat for greater sirens includes vegetative ditches, and various other forms of slow, or stagnant bodies of water. Often during the day, they seek refuges from predators and are found under logs and various other structures.[22]
S. lacertina is difficult to capture because of their preference for areas with thick vegetation. Standard methods such as dip-netting, seining, and dredges are ineffective in such habitats. The use of aquatic funnel traps, commercially produced to capture crayfish, has been found effective for use on Siren and Amphiuma species and there is no risk of drowning the animals. Each trap consists of the trap body, three funnels, and a neck with a lid at the top.[23]
Greater sirens are classified as Least concern by the International Union for Conservation of Nature, although they have been extirpated from some of their former range due to habitat loss. They are protected under Mexican law and are assigned to the "Special Protection" category.[21]
The greater siren (Siren lacertina) is an eel-like amphibian and one of the three members of the genus Siren. The largest of the sirens and one of the largest amphibians in North America, the greater siren resides in the coastal plains of the southeastern United States.
