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. (Conant and Collins, 1991; Hendricks, 2005)
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. (Conant and Collins, 1991; Hendricks, 2005; Leviton, 1971)
- Aquatic Biomes
- lakes and ponds
- rivers and streams
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. (Behler and King, 1979; Conant and Collins, 1991; Hendricks, 2005; Sorensen and Moler, 2008)
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. (Behler and King, 1979; Conant and Collins, 1991; Hendricks, 2005; Sorensen and Moler, 2008)
- Sexual Dimorphism
- sexes alike
- Range length
- 49 to 97 cm
- 19.29 to 38.19 in
- Average length
- 62 - 77 cm
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. (Hendricks, 2005; Sorensen and Moler, 2008)
- Development - Life Cycle
Specifics of greater siren mating systems are unknown. (Hendricks, 2005)
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. (Behler and King, 1979; Hendricks, 2005; Sorensen and Moler, 2008)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Greater sirens breed once yearly.
- Breeding season
- Breeding occurs from February to March.
- Average number of offspring
- 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
Female greater sirens will guard their eggs in the shallows until they hatch and then return to deeper water. No further parental protection occurs. (Hendricks, 2005)
- Parental Investment
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. (Hendricks, 2005)
Greater sirens are strictly nocturnal. During the day, they seek refuge in dense vegetation near the bottom of the bodies of water in which they reside. When these habitats dry up, greater sirens burrow into the mud and secrete a cocoon consisting of dead squamous and epithelial cells. This outer covering prevents water loss. The gills waste away. There are reports of greater sirens living up to 5.2 years in this suspended state, losing nearly 80% of their body mass. However, when water returns, recovery from this aestivation period is rapid. In addition to gills, greater sirens possess lungs and are reported to gulp air at the surface of bodies of water. They also have the ability to perform gas exchange through their epidermis and have been observed crawling out of the water to rest on logs and shores. However, the reduced forelimbs are not suitable for extensive land travel. (Hendricks, 2005; Sorensen and Moler, 2008)
No information is currently available regarding home ranges and territoriality in greater sirens. (Hendricks, 2005)
Communication and Perception
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. (Hendricks, 2005; Sorensen and Moler, 2008)
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. (Fritzsch and Neary, 1998; Hendricks, 2005; Sorensen and Moler, 2008; Sullivan, et al., 2000)
- Communication Channels
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. (Hendricks, 2005; Sorensen and Moler, 2008)
- Animal Foods
- terrestrial non-insect arthropods
- Plant Foods
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. (Hendricks, 2005; Sorensen and Moler, 2008)
- Anti-predator Adaptations
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). (Brooks and Buckner, 1976; Hendricks, 2005; Sorensen and Moler, 2008)
- trematodes (Allassostomoides louisianaensis)
- flatworms (Ophiotaenia sireni)
- flatworms (Progorgodera foliata)
Economic Importance for Humans: Positive
Greater sirens benefit humans by keeping aquatic invertebrate and insect populations in check. (Sorensen and Moler, 2008)
- Positive Impacts
- controls pest population
Economic Importance for Humans: Negative
There are no known adverse effects of greater sirens on humans.
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. (Hendricks, 2005)
Kimberley McKenzie (author), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
- external fertilization
fertilization takes place outside the female's body
union of egg and spermatozoan
mainly lives in water that is not salty.
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
Behler, J., F. King. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Knopf.
Brooks, D., R. Buckner. 1976. Some platyhelminth parasites of sirens (Amphibia: Sirenidae) from North America. The Journal of Parasitology, 62: 906-909.
Conant, R., J. Collins. 1991. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. New York, NY: Houghton Mifflin Company.
Fritzsch, B., T. Neary. 1998. The octavolateralis system of mechanosensory and electrosensory organs. Pp. 878-922 in H Heatwole, E Dawley, eds. Amphibian Biology, Volume 3, Sensory Perception. Chipping Norton, New South Wales, Australia: Surrey Beatty and Sons.
Hendricks, R. 2005. Siren lacertina Linnaeus, Greater Siren. Pp. 141, 361, 364, 372, 644, 911-4 in M Lannoo, ed. Amphibian Declines: The Conservation Status of United States Species. Berkeley: University of California Press.
Leviton, A. 1971. Reptiles and Amphibians of North America. Garden City, New York: Doubleday.
Sorensen, K., P. Moler. 2008. Greater Siren, Siren lacertina. Pp. 263-5 in J Jensen, C Camp, W Gibbons, M Elliott, eds. Amphibians and Reptiles of Georgia. Athens, Georgia: University of Georgia Press. Accessed November 20, 2011 at http://books.google.com/books?id=F4ffa47N9wwC&pg=PA265&lpg=PA265&dq=greater+siren+male+female&source=bl&ots=Fu92LOsFq8&sig=MubvlRASvax-rv7_sTcQcVvzUiA&hl=en&ei=xA-uTpjeJIvYiALAvPmyCw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDAQ6AEwAg#v=onepage&q&f=false.
Sullivan, A., P. Frese, A. Mathis. 2000. Does the aquatic salamander, Siren intermedia, respond to chemical cues from prey. Journal of Herpetology, 34: 607-611.