Taricha granulosa

Reproduction of the Rough-skinned Newt

     Following winter in the spring adult Rough-skinned Newts migrate to breeding ponds. Males arrive ahead of the females, who only come to the pond in limited numbers (Jones et al. 2002, B.C. Frog Watch Program 2013). As discussed in Propper (1991), once both male and female newts have arrived at the pond courtship begins and follows a series of complex behavioral patterns that can be divided into three separate stages: Pre-insemination, insemination and post-insemination. Pre-insemination includes the displayed behaviors that lead to attempted reproduction. Insemination includes the behaviors seen during the fertilization of a female’s eggs and post-insemination includes the behaviors seen after Insemination (Propper 1991).

    The pre-insemination stage is begun by a male newt when he captures a female newt in a position that is known as dorsal amplexus. A visual representation of dorsal amplexus can be seen in the picture on the right side of the page. A description of dorsal amplexus is when a male newt grabs a female so that his fore limbs are behind Rough-skinned Newts in amplexus during the first two stages of reproduction. Used with permission from David Herasimtschuk.her fore limbs and his hind limbs grab her in an area that runs between the abdomen and cloaca (Propper 1991). From here the male newt will move slightly forward and place his lower jaw on her nose in order to rub her submandibular gland in what could be described as chin rubbing (Propper 1991). In addition to the nose rubbing, the male will also quickly flex both hind legs together against the female newt’s abdomen and cloaca (Propper 1991). Around halfway through the hour’s long courtship the female newt will choose to either move her head a small distance from the male newts chin or will continue to remain unresponsive to the male newts mating attempts (Propper 1991). If the male receives this signal from the female newt he will begin the insemination stage by releasing her. Males will almost never attempt to fertilize a female without first receiving this signal (Propper 1991). One reason that the Rough-skinned Newt pre-insemination mating behavior lasts so long is that a female uses this time to evaluate her potential mate for traits such as endurance or competitive ability (Propper 1991). This selection period allows for the female newt to be in control and mate with the most reproductively fit male, which will allow for the highest survival potential in her offspring (Propper 1991, Jones et al. 2002). For the male newts this extra time allows him to decide if a female has previously mated and will therefore be unresponsive to any further mating attempts (Propper 1991).

    A summary of the insemination stage described by Propper (1991) is, once the signal is received by the male he releases the female and moves forward over her head so that he is in front of her and both are perpendicular. The female newt then attempts to keep her head positioned by the male’s cloaca while he produces a spermatophore (a protein capsule with a sperm-filled cap; Propper 1991, B.C. Frog Watch Program 2013). Once the spermatophore is produced the male rotates on one of his front limbs, away from the spermatophore. The female then follows the male until her cloaca is near the spermatohpore. She then moves back and forth until the spermatophore sticks to her cloaca. Once the spermatophore has been successfully attatched, the male turns quickly and captures the female once again in the amplexus position. This is where the post-insemination stage will begin (Propper 1991).

    As the post-insemination state begins the pair will remain inactive and potentially stay in amplexus for many hours. The chances of the first mating attempt being successful are very high in Rough-skinned Newts; however, the behavior of post amplexus allows the male to attempt another insemination if he believes the first was unsuccessful (Propper 1991). Post-amplexus can also act as a unique strategy to prevent competition from other newt sperm by acting as a physical barrier against any future courtship by another male (Propper 1991). Once the breeding season has been finished most female newts will not return to breed for another two to three years (Gall et al. 2012).

    The period between the fertilization and depositing of eggs is about two to three weeks during which a female newt typically does not mate again (Propper 1991). Once a female newt is ready to lay eggs she moves around the pond and attaches single eggs to different stems of available vegetation in an attempt to scatter her eggs around the breeding area (B.C. Frog Watch Program 2013). This behavior of egg scattering may actually be a survival advantage for the species since adult newts show no preference in the consumption of newt eggs including those of its own species and since high numbers of adult newts can be found during the breeding season the number of newt eggs could be quickly consumed if they were not scattered or hidden (B.C. Frog Watch Program 2013). Newt eggs typically hatch three to four weeks after being placed in the water and the larval form that hatches carries out metamorphosis in either the upcoming or the following summer, depending on the weather, to reach its adult form (B.C. Frog Watch Program 2013). These new adult newts then head onto land and do not return to breed until a few mating seasons have went by.  On average the Rough-skinned Newt has a life expectancy in the wild of about twelve years (B.C. Frog Watch Program 2013).

    Like many other organisms there are some costs associated with such a long courtship. One of these costs described by Propper (1991) is the investment of time. Investing so much time into one female greatly reduces the total amount of females that a male can fertilize and thus reduce the potential spread of his genetic traits. Generally the model of spending only a little time with multiple females is what most organisms do to maximize their Multiple Rough-skinned Newts in Amplexus. Note the large number of males compared to females. Used with Permission from David Herasimtschuk.reproductive potential; however, this is not the case with the Rough-skinned newt. This is because the sex ratios of the breeding ponds tend to always be skewed toward males resulting in males having to fight over the few available females. This can be seen in the picture on the left side of the screen where multiple males are swarming around only one or two females. If a male were to only spend a little time on trying to mate with a female he would have a good chance of not being able to mate at all due to a lack of female newts that would be available. The male newt may leave that female and never encounter another receptive female for the remainder of the breeding season. This huge difference between female and male numbers has driven Male newt behaviors toward spending large amounts of time on courting only one female. Newts unlike many other species also do not have to worry about the increased predation rate that accompanies long courtships, since they are highly toxic and only have one known predator which the species Thamnophis sirtalis. Both the skewed sex ratio and toxic compounds of the Rough-skinned newt allow for the species to have long and successful mating attempts (Propper 1991).

    Currently there is one major threat to the reproduction of the Rough-skinned Newt. This threat is man-made and caused by salt run-off from roads that run through fresh-water habitats, leading to unnatural salinization (Hopkins et al. 2012). Taricha granulosa is at high risk from this problem because they are amphibians.  This means that their species has permeable skin and eggs, that will because of the fundamental principles of diffusion allow higher concentrations of salt into the body than what is considered to be normal (Hopkins et al. 2012). In an experiment on Rough-skinned newt eggs, the eggs showed that with increasing concentrations of NaCl and MgCl2, the rate at which the eggs hatched with developmental deformities or perished increased greatly (Hopkins et al. 2012). The deformities in newt hatchlings can show a lot of variety and include deformities of the spine, limbs, and organs as well as the formation of cysts (Hopkins et al. 2012). However, currently the species is in no immediate danger of extinction and steps can be taken to reduce salt run-offs from roads. 

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