The eastern newt is reported to have the most variable life history of all North American amphibians (9), with most populations having four main life stages: egg, larvae, eft and adult (2) (3) (4) (7) (9). While the adults and larvae are aquatic, the intermediate eft stage is typically terrestrial (2) (3) (4) (9). Efts are both diurnal and nocturnal, and are known to be more active on rainy days or nights when the ground is moist (9).
The eastern newt is carnivorous at all stages of its life (9). Feeding at night (9), the larvae of this species feed on whatever is most accessible (3), including snails, beetle larvae, clams, mites and crustaceans (2) (3) (9). Eastern newt larvae have also been reported to occasionally eat algae (3). Adult eastern newts use vision and chemical cues to locate prey that can be swallowed whole (9), and eat small aquatic invertebrates (3) such as molluscs, crustaceans, mayflies, worms and leeches (2) (3) (7) (9). In addition, the eastern newt feeds on the eggs and larvae of other amphibians (2) (3) (7) (9), as well as small fish and fish eggs (9). Eastern newt efts also feed on a variety of invertebrates (2) (3).
As a means of avoiding predation, the eastern newt produces toxic secretions from special glands in its skin (2) (3) (6). This toxin is present during all life stages (3), but efts tend to be more toxic than adults (2). Interestingly, the eastern newt carries out a rather spectacular warning display known as the ‘unken reflex’, which involves the amphibian closing its eyes and retracting them inwards before bowing its head and tail upwards so that they almost meet. In this posture, the brightly coloured belly is exposed (3) (9), which warns potential predators of its toxicity (2) (3) (9). Turtles, snakes and large frogs tend to be the main predators of adult eastern newts (2) (3), while raccoons and certain hawk species are known to avoid them (3).
Reproduction in the eastern newt is aquatic (9). The timing of breeding in this species varies with location, usually occurring during the winter and spring (2). The male eastern newt approaches a female and performs a short display which involves undulating his body and tail. If the female is receptive, it will nudge the male’s tail with its snout. This encourages the male to deposit a spermatophore, which the female then picks up with her vent (3). If the female is unresponsive, the male may grab her in amplexus, and fan its tail to waft secretions through the water toward the female (2). This may last several hours before the male dismounts and deposits a spermatophore for the female to pick up (2).
Egg laying in the eastern newt occurs in the spring in many parts of the species’ range (3) (4) (9), but may start in early winter in more southerly populations and carry on into July in northern populations (9). The female eastern newt deposits each egg individually (2) (3) (9), and lays several eggs per day (2) (9) over a period of a few weeks (3) (9), laying between 200 and 375 eggs in total (9). Each egg measures about 1.5 millimetres in diameter (9), and is attached to aquatic plants or other submerged vegetation (1) (2) (3) (4). The eggs incubate for a period of between three and five weeks (2) (3) (9) depending on the water temperature (3), after which time the larvae hatch out (2) (3) (9).
The length of the larval stage of the eastern newt varies across this species’ range, but usually lasts between two and five months, after which time it transforms into an eft (9). Efts migrate away from aquatic habitats to live in forested areas (9), and may spend up to seven years in this stage, although in some areas transformation occurs within two years (2). Efts then migrate from their terrestrial habitats back to aquatic habitats where they become sexually mature and breed (4) (9).
In some populations, there is no eft stage, and the larvae develop directly into adults. These individuals are known as neotenic adults (5) (9). Most eastern newts are thought to live for between 3 and 8 years, although they may live for up to 15 years (9).