Rachel A. Loehman Samantha Cordova Nancy E. Karraker 2023 <div id="divARTICLECONTENTTop"><div class="div0"><div class="row ArticleContentRow"><p id="ID0EF" class="first">Sex ratio is a key demographic characteristic indicative of the condition of populations. Despite over 70 yr of study, researchers have not fully evaluated morphological characteristics that differentiate sex in Jemez Mountains Salamanders (<i>Plethodon neomexicanus</i>; federally endangered). Populations of this endemic salamander, which are distributed in north-central New Mexico, have undergone declines in the past two decades. We assessed morphological characters of 160 preserved<span>&nbsp;</span><i>P. neomexicanus</i><span>&nbsp;</span>specimens, evaluated our ability to infer sex in the field, and tested our ability to determine sex on a subset of preserved specimens. In preserved salamanders with body length (i.e., postcloaca snout–vent length, SVLp) ≥ 55 mm, females exhibited greater total length, trunk length, tail length, and cloaca length, and males exhibited greater precloacal tail width, head length, head width, and head height. We documented weakly female-biased size dimorphism. Females with SVLp ≥ 52 mm had cloacal rugae, whereas males with SVLp ≥ 51 mm had distinct papillose tissue in the cloaca and a cloacal cleft. In an evaluation of 30 preserved specimens, we correctly inferred sex in 97% of salamanders by cloacal characters alone. Of 29 adult salamanders captured in the field, we confidently inferred the sex of 27 individuals (16 females, 11 males) with SVL ≥ 44 mm. Thus, sex of most individuals can be correctly inferred in the field by cloacal characters. This information will aid researchers in better understanding population trajectories of this endangered species.</p></div></div></div> application/pdf 10.1670/21-083 en BioOne Sexual dimorphism in endangered Jemez Mountains Salamanders (Plethodon neomexicanus) article