Plethodon petraeus, Wynn, Highton & Jacobs, 1988, Wynn, Highton & Jacobs

Marvin, Glenn A., 2024, Courtship and Mating Behavior of the Rare, Rock-Crevice Dwelling Salamander Plethodon petraeus with a Review for Eastern North American Woodland Salamanders (Amphibia: Plethodontidae), Ichthyology & Herpetology 112 (2), pp. 237-256 : 240-247

Mating season and body size comparisons for P. petraeus

Individuals of P. petraeus courted and mated in the laboratory from early May through early July. Thus, field data ( Jensen et al., 2002) and my laboratory observations indicate that the mating season extends from late winter to early summer. For ten females involved in courtships, six engaged in complete courtships and seven engaged in incomplete courtships. For 12 males involved in courtships, nine engaged in complete courtships and seven engaged in incomplete courtships. For both females and males, there was no significant difference in body length for individuals that engaged in complete versus incomplete courtships (Mann-Whitney rank sum tests: U ¼ 16.5, T ¼ 46.5, P ¼ 0.534 for females; U ¼ 30.0, T ¼ 61.0, P ¼ 0.915 for males). There was no significant difference in body condition for males that engaged in complete versus incomplete courtships (ANCOVA: F ¼ 0.05, P ¼ 0.826 for intercepts; F ¼ 0.13, P ¼ 0.725 for slopes); however, body condition was significantly greater for females that engaged in complete courtships (ANCOVA: F ¼ 6.46, P ¼ 0.029 for intercepts; F ¼ 1.89, P ¼ 0.202 for slopes).

Catalogue of courtship behaviors for P. petraeus

Behaviors exhibited by both sexes.— Nose-tap: Individual taps the nasolabial region of its snout on the substrate, skin of another salamander, or a spermatophore (Supplemental Videos 1 and 29). Move toward: Individual moves toward and its head comes close to (i.e., within about 2.5 cm of) the other salamander (Supplemental Video 2). Move away: Individual moves away until its head is more than about 2.5 cm from the other salamander (Supplemental Video 1). Stationary: Individual does not move away when the other salamander moves toward and comes close or makes contact (Supplemental Video 2). Head contact: Head contacts the head of the other salamander (e.g., cheek-to-cheek or snout-to-cheek contact). Nudge: Individual moves its snout against the lateral parts of the other salamander’s body. Tail arch: Individual arches the tail base. Male often exhibits tail arch during ‘position for TSW’ (Supplemental Video 24) and the TSW (Supplemental Video 38). In response to contact by the male, the female exhibits tail arch before and during a ‘female-first TSW’ (ffTSW; Supplemental Videos 3, 5, 8, and 30). Undulate tail: Individual laterally undulates the tail, usually with tail arch. Male undulates his tail during position for TSW and the TSW, and occasionally during mental-gland sliding, foot dance, or foot shuffle (Supplemental Videos 4 and 24). Female undulates her tail before and during ffTSW (Supplemental Videos 5 and 30), and during ‘position on sperm cap.’ Tail (or body) flex: Individual flexes (i.e., greatly bends) the tail or body. Male flexes his tail during both ‘lead female over spermatophore’ and ‘stationary with tail flexed’ during sperm transfer (Supplemental Videos 28 and 35). Female may flex her tail or body in response to mental-gland contact by the male (Supplemental Videos 6, 7, and 17). Tail straddle: Individual steps astride the tail of the other salamander. Male performs tail straddle during ffTSW (Supplemental Video 8). To initiate the TSW, the female performs tail straddle in response to position for TSW by the male (Supplemental Video 9). Bite: Individual bites the other salamander (Supplemental Videos 10, 11, and 25).

Groups and species of eastern Plethodon

Behaviors PCG PWG PGG ci ri we an do yo ke pe ou ca Sh cy mo 1. Nose-tap, 2. Stationary, 3. Move away FM FM FM FM FM FM FM FM FM FM FM FM FM 4. Move toward, 5. Head contact, 6. Nudging FM FM F*M FM F*M F*M FM F*M F*M F*M F*M F*M F*M 7. Bite – – – – – – F*M F*M M – M – M 8. Foot dance – – – – – M* M M d M M F*M M F*M 9. Foot shuffle F – – M M – – M* – – – – – 10. Tail wagging FM FM M FM FM – – – – – – – – 11. Rubbing/sliding, 12. Head rubbing FM FM – FM M – – – – – – – – 13. Head swinging M M – – – – – – M M – – – 14. Joint head swinging – D* – – – – – – – – – – – 15. High amplitude head swinging F F – – – – – – – – – – – 16. Cloacal nudging FM FM – FM – – – – – – – – – 17. Cloacal rubbing F? –? – – – – – – – – – 18. MG sliding (head sliding) M M M M M M M M M M M M M 19. MG popping – – – – – – M* M M* – M* M* M* 20. MG tap or swipe on snout before 42 – – – – M – M – – – M* M* M* 21. MG tap or swipe not on snout – – – – – – M* M* – – – – – 22. Tail (or body*) flex in response to 18 – – – – – – – F – – – – – 23. Tail arch, 24. Undulate tail FM FM M FM M M F*M FM M M F*M M F*M 25. High amplitude tail undulations F F –? – – – F – – – – – 26. Snapping M M – – – – – – – – – – – 27. Pulling M FM? – – – – – – – – – – – 28. Mouth grasping – – – – – – – M – – – M – 29. Snout high – – – – – – F* F – – – – – 30. Chin-to-chin – – – – – – D – – – D* – – 31. Tail straddle for 32 or 33 M M – M M* – – M – – – – – 32. Discontinuous, female-first TSW – – – – – – D d* D – – – – – 33. Continuous, female-first TSW D D – D D* – D d* D – – – – – 34. Turn back during 18, 32, or 33 F F – F – – F F – – F* – F* 35. Circling D D – D – – D d* D d – – – – – 36. Snout under (lifting, crossing under) M M M M M M M M M M M M M 37. Raise chin in response to 36 or before 38 F F F F F F F F F F F F F 38. Chin over F F – F F F* F F F*? F* F* F* 39. Position for TSW M M M M M M M M M M M M M 40. Turn around after 39 or 53 M? M M M M M M M M M M M 41. Tail straddle to initiate 42 F? F F F F F F F? F F F 42. Tail-straddling walk D? D D D D D D D? D D D 43. Turn back during 42 M*? – M

* –

M M – –? M M M 44. Raise head to receive 45 –? – – – – F – –? F – F 45. MG slapping on snout during 42 –? – M* – M M – –? M M M 46. Vent sliding at end of 42 –? – – – M M M M? M M M 47. Spermatophore deposition M? M M M M M M M? M M M 48. Lateral head movements during 47 –? F* – – – – – –? F* – F* 49. Lead female over spermatophore D? D D D D D D D? D D D 50. Pass by spermatophore F?? F F* F* F? F*? F* F* F* 51. Stop & lower vent, 52. Position on cap F? F F F F F F F? F F F 53. Stationary with tail flexed M? M M M M d M M M? M M M 54. Eat spermatophore cap and/or base –? – – M – M M M? M – M Species reference number for source(s) 1 2 3 4 5 6 7 8 9 10 11 12 13

Behaviors exhibited by males only.— Foot dance: While stationary or moving very slowly toward the female with his venter in contact with the substrate, the male repeatedly raises and lowers his fore- and hind-limbs one at a time (Supplemental Videos 4 and 12). Foot shuffle: While stationary and close to the female, male alternately raises and lowers each rear foot (Supplemental Videos 13 and 14). Due to the inability to see the male’s forelimbs clearly on occasions, I report the total occurrence of foot dance and foot shuffle as foot dance/shuffle. Mental-gland sliding: Male slides his mental gland on the female’s skin (Supplemental Video 15). The equivalent behavior in other EP is often termed ‘head sliding’ (e.g., Arnold, 1972). On rare occasions, the male arches his head and may exert downward pressure during sliding (Supplemental Video 16). Male may perform foot dance, foot shuffle, tail arch, and undulate tail during sliding. Mental-gland pop: Occasionally during mental-gland sliding, when the male or female breaks contact, the mental gland abruptly pops away from the female’s skin (Supplemental Videos 15, 17, and 18). The abrupt motion appears as if due to the breakage of an adhesive force. Mental-gland tap: Male taps his mental gland on the female’s skin (Supplemental Video 19). However, unlike some other EP, male does not tap his mental gland on her nares. Mental-gland swipe: Male quickly swipes his mental gland on the female’s skin (but not nares) with a sideways or backward motion (Supplemental Video 20). Mouth grasp: Male lightly grasps the female’s head, body, leg, or tail with his jaws and maintains the grasp for one to several seconds (Supplemental Videos 21 and 22). Snout under: Male positions his snout under the slightly raised chin, body, or tail of the female (Supplemental Video 23). If he raises his head and makes contact with her chin, then she typically raises her chin higher to avoid the contact. Male then slowly crawls under her raised head and positions his tail base beneath her chin. Similarly, if there is sufficient space beneath the female’s body or tail, then the male may perform snout under to the body or tail. ‘Lifting’ and ‘crossing under’ are the equivalent or very similar behaviors described in other EP (e.g., Arnold, 1972; Dyal, 2006). Position for TSW: If the female contacts the male either incidentally when moving or directly by tapping her chin on the male’s dorsum during ‘chin over,’ then the male reflexively positions his arched tail beneath the female’s chin (or against her body or tail) while slowly undulating his tail laterally (Supplemental Video 24). Sometimes the male walks forward very slowly with tail arched and undulating as he maintains contact with the female’s skin. ‘Stationary with tail arched and undulating’ and ‘moving forward with tail arched and undulating’ are the equivalent or very similar behaviors described in other EP (e.g., Arnold, 1972). Turn around: After position for TSW, if the female does not move to maintain contact with the male’s tail, then he typically turns around very slowly toward her with a U-shaped bend of his body, and moves toward her while often performing foot dance with tail arch and undulations. Also, turn around often follows ‘position on sperm cap’ by the female, but he does not perform foot dance or tail arch and undulate (Supplemental Videos 11 and 25). Vent sliding: During the final few seconds of TSW, the male lowers his vent and slides it in contact with the substrate before he stops walking forward (Supplemental Video 26), which may allow him to find an appropriate site to deposit the spermatophore ( Arnold, 1972). Spermatophore deposition: Male stops walking at the end of TSW and remains stationary with his venter and vent in contact with the substrate and his head elevated (Supplemental Video 26). He continues to undulate his tail laterally as the female maintains chin contact with his tail base. Male’s tail undulations increase in frequency and amplitude during spermatophore deposition. Male then stops undulating his tail, arches it upward, and lifts his vent free of the spermatophore (Supplemental Video 27). Stationary with tail flexed: If the female stops and lowers her vent on or near the spermatophore (during ‘lead female over spermatophore’), the male stops walking and, while stationary with his tail flexed, extends and flexes his hind-legs (i.e., performs ‘pelvic lifting’) as she maintains her chin contact with his tail base (Supplemental Video 28). Male eventually stops flexing his rear legs and remains motionless with his rear legs extended and tail flexed to one side. Eat spermatophore: If the male locates an intact spermatophore or the gelatinous base of a spermatophore via nose-tapping, then he typically eats the sperm cap and/or base (Supplemental Video 29).

Behaviors exhibited by females only.— High-amplitude tail undulations: When the male’s chin contacts the female’s tail or sacral region, she may undulate her tail in a slow, wavelike motion while her tail is either in full contact with the substrate or with the tail base arched (Supplemental Video 30). Snout high: Female raises her snout high above the substrate such that her head forms about a 60 to 808 angle with the substrate (Supplemental Video 31). Snout high occurs occasionally in response to mental-gland sliding or during ffTSW. Turn back: As the male rests his mental gland on the female’s tail base, she turns back toward him with a U-shape bend of her body (Supplemental Video 32). Turn back may occur during mental-gland sliding or ffTSW. Such behavior during ffTSW is very similar to the ‘circling’ behavior of some EP ( Dyal, 2006); however, the female does not straddle the male’s tail immediately after turn back. Raise chin: Female raises her chin before or after turn back, or in response to snout under by the male (Supplemental Video 23). Chin over: Female positions her snout above the male and usually taps her chin once or several times on his dorsum. Chin over typically occurs after turn back by the female (Supplemental Video 33) but may also occur in response to snout under by the male (Supplemental Video 34). Male typically responds to such contact with position for TSW. Stop and lower vent: During ‘lead female over spermatophore,’ the female stops walking forward and lowers her vent onto or close to the spermatophore (Supplemental Video 35). Position on sperm cap: After lowering her vent onto the sperm cap of a spermatophore, the female slightly undulates the base of her tail laterally (Supplementary Video 28). Female may or may not successfully retrieve the sperm cap. If successful, she retains the sperm cap in her cloaca as she raises her vent off the gelatinous base. Female may move away immediately after sperm-cap retrieval while male remains stationary with tail flexed.

Duet behaviors with both female and male actions.— Continuous, female-first TSW (ffTSWc): While the male straddles the female’s tail and continually rests his mental gland on her tail base or sacral region, the pair slowly walks forward in tandem as she laterally undulates her tail base continuously beneath his chin (Supplementary Videos 5 and 36). Female may keep her tail base very slightly arched as the pair walks forward without breaking contact. Pair performs tight turns to avoid obstructions (e.g., side of courtship arena) during ffTSWc. Discontinuous, female-first TSW (ffTSWd): Behavior is similar to ffTSWc, but contact between the pair, the forward movement of the pair, and the female’s tail undulations are discontinuous. The female’s walking is sporadically faster than the male’s, which causes his chin contact to break; however, she stops moving forward after taking a few steps. Female’s tail undulations and forward movement only occur when the male’s chin rests on her sacral region or tail. In contrast to ffTSWc, lateral undulations of the female’s tail are less frequent and larger in amplitude, which may cause the male’s chin contact to break. In addition, flex or arch of the female’s tail is typically greater. When the male’s chin contact is lost, it often takes several seconds to re-establish contact (Supplemental Video 37). In some courtships, the pair may transition from ffTSWd to ffTSWc and vice versa. Tail-straddling walk: Following position for TSW, if the female steps astride the male’s tail (Supplemental Video 9), the female walks slowly forward in tandem with the male while continually resting her chin on his tail base. Male continuously undulates his tail base laterally beneath her chin and keeps his tail base arched and head elevated above the substrate as the pair walks forward (Supplemental Videos 36 and 38). Male apparently adjusts his walking speed in response to the position of the female’s chin on his tail (i.e., he walks more slowly if she contacts his tail more distally and vice versa). Pair performs tight turns to avoid obstructions (e.g., side of courtship arena) during TSW. Lead female over spermatophore: Female rests her chin on the male’s tail base as he walks forward after spermatophore deposition with his vent raised and tail flexed to one side. Female walks over the spermatophore with her venter raised just high enough that the sperm cap slightly touches her venter (Supplemental Video 35).

Temporal organization of courtship, behavior frequency, and behavior duration for P. petraeus

Initial courtship encounters.— The ethogram summarizes many of the transitions between behaviors during courtship and mating in P. petraeus ( Fig. 1 ). Initially the male nose-tapped the substrate frequently as he explored the courtship arena. When the male located the female, he often kept his venter in contact with the substrate as he moved toward her very slowly. During initial encounters, the male typically nose-tapped the female’s tail. A male likely identifies the species, sex, and reproductive status of another salamander by olfaction during nose-tapping ( Arnold, 1976; Dawley, 1984; Dantzer and Jaeger, 2007a, 2007b). If the female were non-receptive, she would move away from the male when he contacted her ( Fig. 1 ). The male typically would soon relocate the female visually if she were moving or otherwise via olfaction. The male kept moving toward and contacting a non-receptive female until she eventually remained stationary ( Fig. 1 ). In two incomplete courtships, the male bit the female when he first moved toward her; however, the male soon ceased aggressive behavior and began courtship.

Mental-gland sliding.— During the pre-TSW phase of courtship, the most frequent male behaviors were mental-gland sliding, mental-gland popping, foot dance/shuffle, tail arch, undulate tail, and position for TSW ( Figs. 2 , 3 ). The male typically initiated mental-gland sliding on the female’s tail and then moved very slowly toward her head. If the male initially moved posteriorly during sliding, he would move anteriorly after reaching the tip of her tail. Total duration of sliding per pre-TSW hour was not significantly different between complete and incomplete courtships (two-way ANOVA on ranks, F ¼ 0.22, P ¼ 0.64) but significantly varied among the tail, body, and head (F ¼ 31.06, P, 0.001; Supplemental Fig. A; see Data Accessibility). Duration was greater on the tail than on either the body (t ¼ 6.12, P, 0.001) or head (t ¼ 7.36, P, 0.001; mean ¼ 7.71 6 1.06, 1.91 6 0.37, and 0.73 6 0.15 min/pre-TSW hour, respectively). Mental-gland sliding on the female’s nares was momentary (usually,1 sec) and infrequent (3/10 complete and 5/10 incomplete courtships with mean ¼ 0.27 6 0.06 times/pre-TSW hour; Supplemental Fig. B; see Data Accessibility), since the female would typically turn her head away when the male attempted to contact her snout. On very rare occasions, the female bit the male in response to sliding.

Close, foot dance/shuffle, tail arch, undulate tail, mental-gland pop, and mental-gland tap or swipe.—The male typically remained close to the female when he was not mental-gland sliding ( Fig. 2 ). While close to the female or during sliding, the male would occasionally foot dance/shuffle, tail arch, and undulate tail ( Fig. 3 ). For complete courtships, the male performed sliding and remained close to the female for about 17% and 45% of the pre-TSW phase, respectively ( Table 2 ). For incomplete courtships, the total duration of close per pre-TSW hour was significantly less (Mann-Whitney rank sum test, U ¼ 22.0, T ¼ 133.0, P ¼ 0.038; Fig. 2 ). For all courtships, mental-gland popping occurred often ( Fig. 3 ) when the mental gland lost contact with the female’s skin during sliding. The mean time elapsed before the initial mental-gland pop was 33 6 12 min ( Fig. 4 ). For all courtships, there were significant, positive correlations between the frequency of female undulate tail and both foot dance/shuffle and mental-gland popping ( Table 3 ). For incomplete courtships, there was a significant, positive correlation between the duration of close and the frequency of foot dance/shuffle ( Table 4 ). Mental-gland tap or swipe to the female’s head (but never nares), body, or tail was rare and infrequent (3/10 complete and 2/10 incomplete courtships with mean ¼ 0.71 6 0.42 times/pre-TSW hour; Supplemental Fig. B; see Data Accessibility).

Female tail flex, tail arch, undulate tail, and snout high.— In response to continued mental-gland sliding, the female would eventually perform tail flex, tail arch, and undulate tail ( Figs. 1 , 5 ). Mean time elapsed before the initial tail flex was 72 6 16 min ( Fig. 4 ). For all courtships, there was a significant, positive correlation between the duration of sliding and the frequencies of both foot dance/shuffle and female undulate tail ( Table 4 ). In all courtships, snout high occurred occasionally during sliding ( Fig. 5 ). Mean time elapsed before the initial snout high (118 6 23 min) was similar to that for initial female tail undulations ( Fig. 4 ).

Snout under and position for TSW.— If the female contacted the male either incidentally when she moved or during snout under by the male, then the male reflexively exhibited position for TSW ( Fig. 1 ). Thus, position for TSW occurred frequently ( Fig. 3 ), including early in the courtship ( Fig. 4 ), and the total duration was more than 10 min per pre-TSW hour ( Fig. 2 ) and thus accounted for about 23% of the pre-TSW phase for complete courtships ( Table 2 ). However, a position for TSW most often did not lead to TSW, and thus the male would typically turn around to continue foot dance/shuffle and sliding ( Fig. 1 ). Occasionally, the male would move away from the female after an unsuccessful position for TSW but would soon relocate the female and continue sliding ( Fig. 1 ). For complete courtships, there was a significant, positive correlation between the total duration of sliding and the total duration of unsuccessful position for TSW ( Table 2 ). For all courtships, there were significant, positive correlations between the frequency of position for TSW and the frequencies of foot dance/shuffle, female undulate tail, and chin over ( Table 3 ). For incomplete courtships, there was also a significant, positive correlation between the frequency of snout under and position for TSW ( Table 3 ). Snout under occurred in 70% of courtships, and the mean time elapsed before its initial occurrence was 176 6 37 min ( Fig. 4 ). The frequency of snout under per pre-TSW hour ( Fig. 3 ) was significantly greater for incomplete courtships (Mann-Whitney rank sum test, U ¼ 13.0, T ¼ 68.0, P ¼ 0.005).

Female-first tail-straddling walk.— In most courtships (19/20), the male would eventually (i.e., when female tail undulation occurred upon mental-gland contact to her tail base) step astride the female’s tail during sliding, and the pair would engage in ffTSWd ( Fig. 1 ). Mean time elapsed before the initial ffTSWd was 143 6 17 min ( Fig. 4 ). The number of ffTSWd per pre-TSW hour did not significantly differ between incomplete courtships (mean ¼ 1.66 6 0.44, median ¼ 1.03, range ¼ 0.17 to 4.07) and complete courtships (mean ¼ 1.09 6 0.26, median ¼ 0.95, range ¼ 0 to 2.53; Mann-Whitney rank sum test, U ¼ 40.0, T ¼ 95.0, P ¼ 0.473). However, the duration (min) of each ffTSWd during incomplete courtships (mean ¼ 6.24 6 0.59, median ¼ 4.16, range ¼ 0.47 to 41.63) was significantly greater than during complete courtships (mean ¼ 2.91 6 0.32, median ¼ 2.24, range ¼ 0.5 to 10.25; Mann-Whitney rank sum test, U ¼ 2005.0, T ¼ 3495.0, P, 0.001). Thus, the total duration of ffTSWd per pre-TSW hour ( Fig. 2 ) was significantly greater for incomplete courtships (Mann-Whitney rank sum test, U ¼ 15.0, T ¼ 70.0, P ¼ 0.009). For ten randomly selected ffTSWd in ten courtships (five complete, five incomplete), mean walking speed was 10.6 6 0.9 cm /min (range ¼ 5.6 to 13.6).

For all courtships, there was a significant, positive correlation between the frequency of snout under and the duration of ffTSWd ( Table 4 ). For complete courtships, there were significant, positive correlations between the total duration of ffTSWd and the total duration of sliding and unsuccessful position for TSW ( Table 2 ). For complete courtships, there was a significant, positive correlation between the frequency of mental-gland swipe and the duration of ffTSWd ( Table 4 ). In some courtships, the pair would transition from ffTSWd to ffTSWc and vice versa ( Fig. 1 ).

Mean time elapsed before the initial ffTSWc was 215 6 46 min ( Fig. 4 ). Forty-one ffTSWc occurred in seven courtships with a mean duration of 23.89 6 7.16 min (median ¼ 4.57, range 0.65 to 225.43). Mean total duration for ffTSWc was 16.8 6 5.8 min per pre-TSW hour. For seven randomly selected ffTSWc from seven courtships, mean walking speed was 10.3 6 0.5 cm /min (range ¼ 7.1 to 11.7). There was a trend for pairs to engage in ffTSWc more often during incomplete (6/10) than complete courtships (1/10; Fisher’s exact test, P ¼ 0.057). For incomplete courtships, there were significant, negative correlations between the duration of ffTSWc and the frequencies of foot dance/shuffle and mental-gland popping ( Table 4 ).

The female occasionally exhibited snout high during ffTSWd ( Fig. 1 ). Rarely, the female bit the male after turn back during ffTSW ( Fig. 1 ). In many courtships, the female would turn back during ffTSWd or ffTSWc and exhibit raise chin and chin over ( Figs. 1 , 5 ). For all courtships, there was a significant, positive correlation between the frequencies of turn back and chin over ( Table 3 ). Mean time elapsed before the initial chin over was 219 6 34 min ( Fig. 4 ). The frequencies of turn back and chin over per pre-TSW hour ( Fig. 5 ) were significantly greater for complete courtships (Mann-Whitney rank sum tests: U ¼ 17.0, T ¼ 138.0, P ¼ 0.014 for turn back; U ¼ 20.0, T ¼ 135.0, P ¼ 0.025 for chin over). For all courtships, if the female contacted the male during chin over, then the male often exhibited position for TSW ( Fig. 1 ).

Mouth grasp.— Mouth grasping occurred infrequently during four complete and two incomplete courtships (mean ¼ 0.98 6 0.35 times per pre-TSW hour; Supplemental Fig. B; see Data Accessibility) and always occurred at least 200 min after the courtship began ( Fig. 4 ). For incomplete courtships, there were significant, positive correlations between the duration of time apart and the frequencies of mouth grasp and female tail flex ( Table 4 ) and a significant, positive correlation between the frequencies of mouth grasp and female tail flex per pre-TSW hour ( Table 3 ). The female sometimes bit the male in response to mouth grasping.

Initiation and duration of the TSW.— If the female did not step astride (i.e., tail straddle) the male’s tail during position for TSW, then courtship did not proceed to a TSW ( Fig. 1 ). In each complete courtship, female turn back and chin over preceded the first successful position for TSW (i.e., male snout under never preceded the first TSW). However, for the courtship with two TSW, snout under preceded the second TSW. Mean time elapsed before the initiation of TSW was 290 6 66 min ( Fig. 4 ). The duration of most TSW (8/11) ranged from 20 to 32 min (max. ¼ 223, Table 2 ). There were significant, positive correlations between the duration of TSW and the total time apart and the total duration for ffTSW (i.e., both discontinuous and continuous forms combined; Fig. 6 ). Mean distance traveled during TSW was 3.93 6 0.65 m (range ¼ 1.86 to 9.69, n ¼ 11). Mean walking speed during TSW was 12.7 6 1.9 cm /min (range ¼ 1.0 to 23.2).

Spermatophore deposition, sperm transfer, and the duration of complete courtships.—Mean time elapsed before the start of the first spermatophore deposition was 346 6 75 min ( Fig. 4 ). Mean time for deposition was 7.5 min ( Table 2 ). During deposition, the mean frequency of male tail undulations increased from 0.47 6 0.28 Hz at the beginning to 0.84 6 0.28 Hz at the end (range ¼ 0.31 to 0.61 and 0.67 to 0.95, respectively). Mean time for lead female over spermatophore was 0.4 min ( Table 2 ). Mean time for female position on sperm cap (including successful and unsuccessful cap-retrieval attempts) was 0.6 min ( Table 2 ). Females retrieved the sperm cap from 55% (6/11) of spermatophores with a success rate of 60% per courtship ( Table 2 ). In 80% of complete courtships, the male turned around and then bit or aggressively chased (e.g., repeatedly lunged and snapped at) the female either immediately after (4/10 courtships) or within 2 min after (4/10 courtships) position on sperm cap by the female ( Fig. 1 ). For the 11 spermatophores, the male eventually ate the gelatinous base (n ¼ 2), cap (n ¼ 1), or entire spermatophore (n ¼ 3).

The total duration of complete courtships from the first encounter between salamanders until the final attempted retrieval of a sperm cap ranged from 160 to 787 min (mean ¼ 370, Table 2 ). Duration of the pre-TSW phase for these courtships ranged from 39 to 715 min (mean ¼ 245, Table 2 ). Excluding periods when salamanders were apart after their initial encounter, total duration of courtship and mating ranged from 89 to 754 min (mean ¼ 301, Table 2 ).

Figures

FIG. 1. Ethogram for many of the transitions between behaviors during courtship and mating in the salamander Plethodon petraeuS. Data are from 20 individually unique pairs that engaged in ten incomplete courtships, which did not proceed to a tail-straddling walk (TSW), and ten complete courtships with TSW and spermatophore deposition. Line with arrowhead at both ends indicates transition in either direction. A solid line indicates the transition occurred in $65% of courtships, whereas a dotted line indicates the transition occurred in,65% of courtships (with n ¼ 20 and 10 courtships prior to and after female tail straddle, respectively). NT ¼ nose-tap. TA ¼ turn around. Dance/ Shuffle ¼ foot dance and foot shuffle. See text for description of behaviors. *Incidental contact to the male during female movements of her feet, tail, or body often elicited position for TSW well before the occurrence of snout under or chin over. In each complete courtship, female turn back and chin over preceded the first successful position for TSW. Ethogram does not include a few male behaviors (stationary, head contact, tale arch, and tail straddle) and very infrequent female behaviors (nose-tap, move toward, head contact, and nudge).

FIG. 2. Duration of some behaviors and periods during the preliminary (pre-TSW) phase of courtship in the salamander Plethodon petraeuS. Data are from 20 individually unique pairs that engaged in ten incomplete courtships, which did not proceed to a tail-straddling walk (TSW), and ten complete courtships with TSW and spermatophore deposition. See text for description of behaviors. Close ¼ salamanders within about 2.5 cm of each other but not in sustained contact via the mental gland (e.g., includes periods with male foot dance/shuffle, tail undulation, nudging, and snout under). MG Sliding ¼ mental-gland sliding on the skin of the female. ffTSWd ¼ discontinuous, female-first TSW. ffTSWc ¼ continuous, female-first TSW. Position for TSW ¼ attempted male solicitation of TSW. Box plots show minimum, maximum, median (solid horizontal line), mean (dotted horizontal line), and percentiles (10th, 25th, 75th, and 90th). *, **Probability values from Mann- Whitney rank sum tests demonstrate a significant difference between complete and incomplete courtships for the duration of both close and ffTSWd.

FIG. 3. Frequency of some male behaviors during the preliminary (pre-TSW) phase of courtship in the salamander Plethodon petraeuS. Data are from 20 individually unique pairs that engaged in ten incomplete courtships, which did not proceed to a tail-straddling walk (TSW), and ten complete courtships with TSW and spermatophore deposition. MG ¼ mental gland. See text for description of behaviors. Box plots show minimum, maximum, median (solid horizontal line), mean (dotted horizontal line), and percentiles (10th, 25th, 75th, and 90th). *Probability value from Mann-Whitney rank sum test demonstrates a significant difference between complete and incomplete courtships for the frequency of snout under.

FIG. 4. Time elapsed before the first occurrence of some courtship behaviors in the salamander Plethodon petraeuS. Data are from 20 individually unique pairs that engaged in ten incomplete courtships, which did not proceed to a tail-straddling walk (TSW), and ten complete courtships with TSW and spermatophore deposition. See text for description of behaviors. Number within brackets is the number of courtships with the behavior. Box plots show minimum, maximum, median (solid horizontal line), mean (dotted horizontal line), and percentiles (10th, 25th, 75th, and 90th).

FIG. 5. Frequency of some female behaviors during the preliminary (pre-TSW) phase of courtship in the salamander Plethodon petraeuS. Data are from 20 individually unique pairs that engaged in ten incomplete courtships, which did not proceed to a tail-straddling walk (TSW), and ten complete courtships with TSW and spermatophore deposition. See text for description of behaviors. Box plots show minimum, maximum, median (solid horizontal line), mean (dotted horizontal line), and percentiles (10th, 25th, 75th, and 90th). **, *Probability values from Mann-Whitney rank sum tests demonstrate a significant difference between complete and incomplete courtships for the frequency of both turn back and chin over.

FIG. 6. Total duration (min) of some behaviors and periods during complete courtships in the salamander Plethodon petraeuS. Data are from ten individually unique pairs that engaged in complete courtship with tail-straddling walk (TSW) and spermatophore deposition. For Pair 3 courtship, there were two spermatophore depositions, but this figure only includes data from the first spermatophore deposition. A ¼ Courtship duration from initial close encounter between salamanders until the retrieval or attempted retrieval of the first spermatophore cap. B ¼ Total of all periods when salamanders were more than about 2.5 cm apart after their initial encounter. D ¼ Total duration for female-first TSW, which includes both discontinuous and continuous forms of the duet behavior. Pearson Product Moment correlation coefficients: r ¼ 0.882, P, 0.001 for B and D; r ¼ 0.952, P, 0.0001 for B and F; r ¼ 0.964, P, 0.00001 for C and E; r ¼ 0.961, P, 0.00001 for D and F. See Table 2 for additional data on the duration of other behaviors and periods.