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Commensal Nesting of Scincella lateralis (Little Brown Skinks) in Alligator mississippiensis (American Alligator) Nests and Ondatra zibethicus (Muskrat) Houses in Southwestern Louisiana
Ruth M. Elsey, Mickey Miller, Dwayne LeJeune, and Will Selman

Southeastern Naturalist, Volume 15, Issue 4 (2016): 653–668

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Southeastern Naturalist 653 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 22001166 SOUTHEASTERN NATURALIST 1V5o(4l.) :1655,3 N–6o6. 84 Commensal Nesting of Scincella lateralis (Little Brown Skinks) in Alligator mississippiensis (American Alligator) Nests and Ondatra zibethicus (Muskrat) Houses in Southwestern Louisiana Ruth M. Elsey1,*, Mickey Miller1, Dwayne LeJeune1, and Will Selman1 Abstract - Scincella lateralis (Little Brown Skink, hereafter Skink) are ubiquitous throughout the southeastern US and primarily nest in leaf litter on the forest floor. However, their presence in coastal marsh settings necessitates their use of alternate nesting habitats. We investigated Skink nesting ecology in Alligator mississippiensis (American Alligator) nests and Ondatra zibethicus (Muskrat) houses in an intermediate/brackish coastal marsh habitat at Rockefeller Wildlife Refuge in southwestern Louisiana. For our field studies, we found and collected Skink eggs from 16 June through 5 October, and hatched eggshells from 6 July through 5 October. We found Skink eggs/eggshells in 36 of 109 active American Alligator nests (33.0%), 19 of 36 inactive Alligator nests (52.8%), and 13 of 51 Muskrat houses (25.5%). Clutch size ranged from 1 to 5 eggs (average = 3.0). The mean depth of Skink eggs was 24.6 cm in American Alligator nests and 17.1 cm in Muskrat houses. Multiple clutches commonly occurred in a structure, indicating repeated use by a single female Skink or communal nesting. In one extreme case of communal nesting, we collected at least 932 Skink eggs and hatched eggshells from a single Alligator nest. Skink eggs that we measured weekly during a 30-day incubation period increased in length and width. Earliest hatch dates for laboratory-incubated Skink eggs occurred from 28 June through 3 July; the last Skink hatched on 14 October. We documented a hatch rate of 87.6%. Hatchlings (n = 806) had a mean total length of 5.01 cm (n = 23) and a mean snout–vent length of 2.02 cm (n = 18). Our study indicated that Skinks readily nest commensally and communally within coastal marsh Alligator nests and Muskrat houses. Introduction Scincella lateralis (Say) (Little Brown Skink, hereafter Skink) occur commonly and are widely distributed throughout the southeastern US (Conant and Collins 1998, Johnson 1953, Lewis 1951). Typical habitat consists of a thick groundcover of grasses or leaf litter located in or on the edges of fairly dense stands of trees (Clause et al. 2015, Lewis 1951). Skinks have also been noted to inhabit Geomys (pocket gopher) mounds (Funderburg and Lee 1968), marsh berms (J. Boundy Louisiana Department of Wildife and Fisheries [LDWF], Baton Rouge, LA, pers. comm.), coastal chenier forest (Selman 2015), and Alligator mississippiensis Daudin (American Alligator, hereafter Alligator) nests in a coastal marsh (Elsey et al. 2013). Coastal marshes typically contain few trees (Elsey et al. 2015) and are devoid of suitable leaf-litter habitat for Skinks; thus, the recent discovery of Skinks nesting commensally in coastal marsh Alligator nests was noteworthy (Elsey et al. 2013). 1Louisiana Department of Wildlife and Fisheries, 5476 Grand Chenier Highway, Grand Chenier, LA 70643. *Corresponding author - Manuscript Editor: Cathryn Greenberg Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 654 Early publications on Skink reproductive ecology were often based upon examination of museum specimens (Fitch and Greene 1965, Johnson 1953, Lewis 1951). More-recent studies of this species have provided further details on reproduction in field conditions (Mitchell 1994, Palmer and Braswell 1995). Limited data are available on the reproductive biology of Skinks in Louisiana (Arny 1948; Johnson 1953, as noted in Dundee and Rossman 1989; Fitch and Greene 1965; Lewis 1951). In this study, we document the usage rate, clutch size, and timing of Skink nesting and egg deposition in Alligator nests and Muskrat houses in a Louisiana coastal marsh. We incubated eggs collected from commensal nests to definitively determine the species of origin and estimate incubation period. We also attempted to determine if any other reptile species utilized Alligator nests or Muskrat houses as nest sites because many other species have been documented nesting in these structures in other portions of their range (Elsey et al. 2013, Enge et al. 2000, Mathiak 1966, Svihla and Svihla 1931). Methods Study site We conducted this study on Rockefeller Wildlife Refuge, a coastal marsh owned and operated by the Louisiana Department of Wildlife and Fisheries (LDWF). The study site was in the Superior marsh system in Cameron Parish (Fig. 1)—a marsh habitat of intermediate to brackish salinity (less than 10 ppt) and a site for a longterm Alligator nesting study (Elsey 1996, Joanen and McNease 1987). The habitat is dominated by several marsh plant species such as Spartina patens (Aiton) Muhl. (Saltmeadow Cordgrass), Phragmities sp. (common reed), and Typha sp. (cattail) with interspersed bayous and ponds throughout (Joanen 1969). The southern end of the system is impounded by a ring levee and water-control structures to limit excessive saltwater intrusion from Gulf of Mexico inlets. Thus, although the system is proximate to the Gulf of Mexico, water levels are typically driven by rainfall events occurring throughout the Mermentau River Basin of south-central Louisiana rather than by tidal influxes. Field study We searched for Alligator nests and Muskrat houses by helicopter on 15 June 2015. We recorded nest locations on a handheld GPS and marked them with a 3.05- m PVC pipe for later visits by airboat. Starting on 16 June, we manually opened the compact vegetation comprising the Alligator nests and Muskrat houses to search for the presence of Skink eggs (or eggs of any other species). The structures occurred in the same habitat; thus, vegetation used for construction of both Alligator nests and Muskrat houses was similar. We classified Alligator nests containing Alligator eggs as active; nests without Alligator eggs might have been false nests, incompletely constructed nests, or nests that were abandoned (hereafter, inactive). We measured or estimated the depth of the Skink eggs within individual Alligator nests or Muskrat houses to the nearest inch (2.54 cm). After removing Alligator eggs (if present) for other studies, we attempted to restore the nest vegetation to its original shape. Southeastern Naturalist 655 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 We initially planned to check each structure once each month (June–August); however, unusually dry conditions in July limited airboat access to field sites and results during the early phase of the study led us to continue checking Alligator nests and Muskrat houses into September and early October. Figure 1. Map of the study site on portions of Rockefeller Wildlife Refuge in Grand Chenier, LA. Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 656 In many cases, we recovered more than 1 clutch of Skink eggs from Alligator nests or Muskrat houses. We classified a nest/house as used either repeatedly, or by more than 1 Skink (communal nesting) if 1 of the following criteria were met: (a) >7 unhatched eggs present at any site visit, (b) eggs of markedly different sizes/ ages (which hatched at widely separated times) present at any one visit, (c) unhatched eggs or eggshells present at separate nest-checks conducted weeks apart, or (d) new unhatched eggs plus hatched eggshells present at any evaluation. The first 2 criteria above would only be met if more than 1 Skink used the structure; the last 2 criteria might indicate use by the same female depositing a second clutch. We collected Skink eggs and placed them in labeled zip-lock bags or plastic specimen-cups (120 ml [4 oz.]) half-filled with vermiculite, and secured in a plastic tote for transport back to the field-laboratory incubato r. We consider 1 sampled nest to be an outlier and an extraordinary case of communal nesting. This Alligator nest (hereafter termed the “drone nest”) was discovered on 23 June as part of a separate study to determine the effectiveness of drones for locating Alligator nests (Elsey and Trosclair 2016). When we opened the drone nest to determine if Alligator eggs were present, we discovered numerous groups of Skink eggs and subsequently checked the nest approximately every 2 weeks until 5 October. Laboratory incubation study We incubated Skink eggs in controlled environmental chambers used for Alligator egg culture (Joanen and McNease 1976) to allow positive species identification and provide information on minimum incubation period for this site. We used plywood boards to create racks to hold containers above water heated to 31–33 oC to maintain high humidity; surrounding air temperatures were lower. We placed Skink eggs in a variety of plastic containers, initially with a base layer of natural vegetation from the Alligator nest (usually Saltmeadow Cordgrass), and covered with a small amount of similar natural vegetation. We soon found Skink eggs were held in place more securely when placed upon a base layer of slightly damp vermiculite and covered with natural nest vegetation. Plastic containers ranged in size based on the quantity of Skink eggs found in each nest, and included 120-ml specimen cups, plastic “stadium” drinking cups, small food-storage containers, 2.27 L (0.6 gallon) tubs, and plastic totes (29.2 cm L x 19.7 cm W x 16.5 cm H or 40.6 cm L x 29.2 cm W x 16.5 cm H). We checked Skink eggs approximately every other day from the date of collection until we anticipated hatching might begin, then checked them daily from 6 July through 14 October (except 12 and 26 July). We recorded clutch size for all nests, but we encountered numerous cases of what we assumed was communal nesting because egg quantity often exceeded previously reported clutch sizes for the species, and some eggs appeared to be of differing sizes (suggesting they were of different ages or stages of incubation). Thus, in calculating clutch-size ranges, we only used clutches in which all eggs hatched on the same day and those that hatched over 2 days (presumably from a single clutch). It is likely that other single clutches hatched eggs across multiple Southeastern Naturalist 657 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 days; therefore, our estimates are probably conservative. Nests with hatched Skink eggshells were omitted from clutch-size estimates because we had no way to determine hatch dates. To monitor Skink egg growth during incubation, we measured 4 clutches of small eggs (i.e., believed to be close to the time of oviposition when collected). We measured eggs (length and width; mm) with digital calipers on the day of collection (3 clutches on 29 July, and 1 clutch on 12 August), and weekly thereafter until hatching. When incubation was completed, we measured the total length (TL) and snout– vent length (SVL) of live hatchlings and immediately released them at the field laboratory site. Statistical analyses We used chi-squared analysis to test for differences in the presence of Skink eggs/eggshells between Alligator nests (active or inactive) and Muskrat houses. We also tested for differences in eggs/eggshells between active and inactive Alligator nests. The distribution of the sum of Skink eggs per structure was non-normal, and we could not transform the dataset to meet parametric assumptions of normality. Therefore, we used nonparametric Wilcoxon ranked sum tests with chi-squared approximation to determine if the mean sum of Skink eggs was equal for Alligator nests and Muskrat houses, and for active and inactive Alligator nests. We excluded the drone nest from all statistical analyses as an extreme outlier. We used JMP 9 for all statistical analyses (SAS Institute, Inc. 2010) and set statistical significance at P < 0.05. Results Field study We found and searched a total of 145 Alligator nests (109 active and 36 inactive) and 51 Muskrat houses. Skink eggs or hatched eggshells were present in 37.9% (55 of 145) of all Alligator nests and 25.5% (13 of 51) of Muskrat houses; these proportions were not significantly different (χ2 = 2.58, df = 1, P = 0.11). Skink eggs or hatched eggshells were found significantly more often in inactive Alligator nests (52.8%, 19 of 36) than active Alligator nests (33.0%, 36 of 109; χ2 = 4.48, df = 1, P = 0.03). All suspected Skink eggs incubated and hatched in the field incubator produced S. lateralis hatchlings; we presume that hatched eggshells recovered in the field were of the same species. We first observed Skink eggshells in Alligator nests on 6 July, and we recovered hatched eggshells at the final check on 5 October. We were unable to determine precise peak nesting and hatching dates, due to irregular sampling effort, and inability to determine oviposition dates for unhatched eggs and hatched eggshells. However, the frequency of nests/houses containing Skink eggs peaked between mid-July and mid-August (Fig. 2). The depth at which Skink eggs were buried (mean ± SE) within Alligator nests was 24.6 ± 3.2 cm (range = 5.1–61.0 cm, n = 18 nests). The mean depth for Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 658 5 clutches of Skink eggs found in 4 Muskrat houses was 17.1 ± 8.9 cm (range = 12.7–61.0 cm). The average (mean ± SE) number of Skink eggs/eggshells (excluding those with zero counts) in Alligator nests was 10.1 ± 8.3 (range = 1–52, n = 55) and 9.8 ± 5.5 (range = 3–26, n = 13) in Muskrat houses; means did not significantly differ (χ2 = 0.61, df = 1, P = 0.43). Active Alligator nests contained a mean of 8.9 ± 7.4 Skink eggs/eggshells (range = 1–52, n = 36) and inactive Alligator nests had a mean of 12.4 ± 10.0 Skink eggs/eggshells (range = 1–51, n = 19); means did not significantly differ (χ2 = 0.22, df = 1, P = 0.63). In at least 7 cases, we documented large numbers of Skink eggs in Alligator nests or Muskrat houses, which suggested repeated use by a single female or use by multiple female Skinks (i.e., egg quantities exceeded the maximum reported clutch size of 7 for a single female [Fitch and Greene 1965]). We also documented large quantities of Skink eggs and hatched eggshells at some sites, in excess of what a single female would produce if it nested 4–5 times in a season (Fitch and Greene 1965). For these 32 sites, the eggs/eggshell production (mean ± SE) was 14.9 ± Figure 2. Peak of Skink nesting as estimated by percent of structures (Alligator nests or Muskrat houses) that contained Skink eggs over time. The zeros in the figure indicate days on which we found no structures with Skink eggs present. The smooth line is the mean number of structures occupied over time. Southeastern Naturalist 659 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 3.1 (range = 5 – 52, n = 17) for active Alligator nests, 22.4 ± 4.9 (range = 6–51, n = 9) for inactive Alligator nests, and 16.3 ± 3.0 (range = 8–26, n = 6) for Muskrat houses. There were no significant differences in their eggs/eggshell production between structure types (χ2 = 0.84, df = 1, P= 0.36) or between active and inactive Alligator nests (χ2 = 3.17, df = 1, P = 0.07). In 6 other cases (not counting the drone nest site), we collected eggs of visibly different sizes; these were almost certainly of different ages and thus deposited by more than one female. Details on the timing, composition, and total egg/eggshell production for some of the communal sites, including the the drone-nest site, where we observed at least 650 Skink eggs and 282 hatched eggshells (total production of 932)—in addition to 34 Alligator eggs—in 9 site checks from 23 June to 5 October, are presented in Tables 1 and 2. We only observed live adult Skinks (2 individuals, species not confirmed) once, on 24 August while collecting Skink eggs at the drone nest. We observed a single hatched Thamnophis p. proximus (Say) (Orange-striped Ribbon Snake) egg in an active Alligator nest, and 5 Lampropeltis holbrooki Stejneger (Speckled Kingsnake) eggs in another; we observed a single Speckled Kingsnake egg in 1 inactive nest and 6 hatched eggs of an unknown snake species in another. We found no snake eggs in Muskrat houses, and no eggs of turtles or other lizard species were found in either structure type. Laboratory incubation study Of 14 apparent clutches (groups of eggs found clustered and hatching the same day), the mean (± SE) clutch size was 3.00 ± 0.41 eggs (range = 1–5). There were 10 additional cases in which all Skink eggs hatched over a 2-day period; including those groups, mean clutch size was 3.17 ± 0.29 eggs (range = 1–5; n = 24). Within-clutch lengths and widths of viable eggs increased 8–14% throughout incubation (Figs. 3, 4). The earliest hatch date for incubated eggs occurred between 28 June and 3 July, and the last Skink, which was from the drone nest, hatched on 14 October (Table 2). Minimum known incubation period was 30 days to hatching. Hatching success was 87.6% (806 of 920 eggs). In 28 clutches, 100% of the Skink eggs incubated from individual Alligator nests or Muskrat houses hatched. Causes of egg failure (43 unhatched eggs) were attributed to desiccation/collapse (n = 17), Table 1. Summary of some sites exhibiting communal Skink nesting based on quantity of eggs and/or eggshells recovered. The “drone nest”, another communal nesting site, is detailed in Table 2. Nest site Site type Date Eggs Eggshells Total Other 71 Alligator, active 9 Jul 47 52 Plus 5 eggs on 25 June 113 Alligator, inactive 22 September 4 47 51 159 Alligator, active 17 September 38 38 102 Alligator, inactive 17 August 22 12 35 Plus 1 eggshell 22 September 11 Alligator, inactive 1 October 33 33 166 Alligator, inactive 17 September 8 18 26 137 Muskrat 22 September 17 6 23 Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 660 Table 2. Summary table for Skink eggs and hatched eggshells recovered from an extraordinary case of communal nesting in an active Alligator nest in 2015 on Rockefeller Wildlife Refuge in coastal Louisiana. Large Small Hatched Total day’s Date Trip eggs eggs eggshells Other eggs Remarks Hatch days 23 June 1 21 20 1 medium egg 42 2 eggs left at nest not counted Large = ~3–18 July, small = 16–17 July 8 July 2 55 65 24 5 bad eggs discarded 149 A few other eggs and eggshells Large = 12/13–28 July, lost both sizes = 20 July–4 August, small = 15 July–3 August 16 July 3 62 21 63 7 unsure if viable incubated 158 Plus 5 bad eggs discarded Both sizes = 24 July–12 August 29 July 4 16 43 9 4 dessicated incubated 72 Large = 9–21 August, medium/small = 11–25 August 12 August 5 34 54 32 120 Large = 17 August–3 September, medium/small = 22 August–8 September 24 August 6 54 21 52 2 flooded discarded 129 Large = 13–17 September, small = 15–20 September 9 September 7 56 34 21 111 Some ants in nest Large/medium = 16 September–2 October, small = 27 September–3 October 22 September 8 69 0 59 128 No small/medium eggs Very large = 27–30 September, large = 26 September–6 October 5 Oct 9 1 0 22 23 No small/medium eggs 14 October Total 932 Southeastern Naturalist 661 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 embryonic death (n = 14), infertility (n = 3), researcher egg examination (n = 2), or unknown (n = 7). Newly hatched Skinks had a mean (± SE) TL of 5.01 ± 0.06 cm (range = 4.6–5.6 cm, n = 23) and an average SVL of 2.02 cm ± 0.02 (range = 1.9–2.2 cm, n = 18). Figure 3. Weekly mean length (mm) of Skink eggs during incubation. We measured eggs when collected (time 1) and weekly thereafter (time 2, 3, and 4). Individual clutches are identified (126, 207, 224, and 48 B). Error bars are ± 1 standard error. Figure 4. Weekly mean width (mm) of Skink eggs during incubation. Eggs initially measured when collected (time 1) and weekly thereafter (time 2, 3, and 4). Individual clutches are identified (126, 207, 224, and 48 B). Error bars are ± 1 standard error. Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 662 Discussion Field study Alligator nests serve as commensal nesting sites for several reptiles in Louisiana (Elsey et al. 2013) and other areas throughout the Alligator’s range (Brandt and Mazzotti 2000, Deitz and Jackson 1979, Enge et al. 2000, Kushlan and Kushlan 1980a). To our knowledge, the present study employed the largest sample size to document commensal nesting by Skinks in Alligator nests and Muskrat houses. Our findings also contribute to further understanding of numerous aspects of the nesting ecology of Skinks. The relatively high occurrence of commensal nesting by Skinks was unexpected because their preferred habitat is within forest leaf-litter rather than coastal marsh. However, Skinks have been documented in southern Louisiana marshes (Arny 1948, Dundee and Rossman 1989) and upland chenier forest habitat Selman (2015). We found a slightly higher occurrence of commensal nesting by Skinks in Alligator nests (37.9%) compared to an earlier study with a very small sample-size (33.3%, 2 of 6 nests; Elsey et al. 2013). Similar to Elsey et al. (2013), we found Speckled Kingsnake eggs in Alligator nests, as well as a new record of an Eastern Orange-striped Ribbon Snake egg. We found more Skink eggs in inactive than active Alligator nests. Similarly, Enge et al. (2000) reported that nesting turtles used inactive (vacant) Alligator nests for egg deposition more often (63.6%) than active (occupied) Alligator nests (36.1%). The reasons for this are unclear; it is possible that Skink eggs would be less disturbed in inactive Alligator nests because Alligators often add nesting material (vegetation) to the structure during incubation (Deitz and Hines 1980), potentially displacing Skink eggs and leading to clutch failure. It is also plausible that Skinks may use chemosensory cues to detect the presence of Alligator eggs or the nearby female Alligator and avoid active nests in preference to inactive nests or Muskrat houses. Although Skink eggs had not been documented in Alligator nests until recently (Elsey et al. 2013), several studies have noted limited use of Alligator nests by Anolis carolinensis Voigt (Green Anole; Brandt and Mazzotti 2000, Deitz and Jackson 1979, Kushlan and Kushlan 1980a). Our study also documented Skink use of Muskrat houses as sites for egg deposition. Muskrat houses are used by numerous species for nesting, including Skinks in Louisiana marshes (Svihla and Svihla 1931), Chelydra serpentina L. (Common Snapping Turtle; Mathiak 1966) in Wisconsin, and Chrysemys picta (Schneider) (Painted Turtle; Adams 1925) in New York. The range of depths where we found Skink eggs in both Alligator nests and Muskrat houses was highly variable in our study and appeared similar. Skink eggs were not usually within the same egg cavity as the Alligator eggs, if the latter were present. Little information on Skink egg depth is available in the literature, but Lewis (1951) noted 1 Skink nest that was ~2.5 cm below soil and leaves. We found Skink eggs in Alligator nests and Muskrat houses from mid-June through 5 October (in an Alligator nest); this observation extends the nesting season later than previously documented. Johnson (1953) reported that female Skinks Southeastern Naturalist 663 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 had oviductal eggs in every month from March through August, with egg-laying peaking in May, June, and July. He also noted that Skinks simultaneously contained both oviductal eggs and enlarging follicles, suggesting the potential for 2 clutches per season (Johnson 1953). Others have reported an interval of perhaps 5 weeks between successive clutches in Gulf Coast Skinks, suggesting there is ample time for at least 4 or even more broods during a single reproductive season (Fitch and Greene 1965). We could not determine clutch frequency in our study, but high reuse of the same nest sites suggested that multiple clutches per female was likely. Fitch and Greene (1965) reported that June is the peak of the Skink breeding season in the southern part of the range, but first clutches are deposited from late April through May. In our study, the proportion of structures with Skink eggs remained high from late June until mid-August. Alligator nests are typically constructed in southwestern Louisiana in mid- to late June (Joanen 1969). Therefore, Alligator nests may not be available as nesting sites for Skinks until mid-summer, and Skinks may use alternate nesting sites earlier in spring. We first recovered hatched Skink eggshells in an Alligator nest on July 6; if incubation is ~30 days, these eggs might have been deposited around June 6, or earlier. We were unable to address the possibility that Skinks nested in Muskrat houses before Alligator nest-building was initiated in mid-May and June, but it seems possible because Louisiana Muskrat reproduce and use houses yearround (Boutin and Birkenholz 1987, O’Neil 1949). Oviductal eggs have been found in Skinks as early as 25 March in Mississippi (Cook 1943), and Skink nests have been found as early as 12 May in Louisiana (Johnson 1953). If Skinks used Muskrat houses for egg deposition earlier in the spring (April–early June), one would expect to recover Skink eggshells in early summer; we did not find hatched eggshells in Muskrat houses until 12 August. Future studies might be warranted to determine if Muskrat houses are used for Skink egg deposition earlier in spring. Although the latest oviposition date previously reported for the species was 28 July (Arny 1948), Johnson (1953) suggested eggs might be deposited as late as September because oviductal eggs were observed in August (Dundee and Rossman 1989, Johnson 1953). The Skink eggs collected in our study on 5 October (1 of which hatched on 14 October) corroborates the suggestion that Skinks can lay eggs in September (Johnson 1953). The 14 October hatch date would suggest an approximate oviposition date of mid-September, the latest egg deposition date reported for the species. It is likely that southern portions of the species’ range (including our study area) support a longer nesting season than northern sites. Arny (1948) and Mitchell (1994, for Virginia) reported field-collected nests hatched during July and August. In our coastal Louisiana study, 8 clutches hatched in October, as did numerous eggs collected from the drone nest-site. Observational data on communal egg-laying are scarce (Garcia-Roa et al. 2015), despite being an apparently common behavior in lizards (Doody et al. 2009). Communal nesting might result from a scarcity of suitable nest sites (constraint) or be adaptative, by increasing fitness (Radder and Shine 2007). Others have reported communal nesting by Skinks (Gibbons et al. 2009; C.A. Pague, Old Dominion Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 664 University, Norfolk, VA, pers. comm., as noted in Mitchell 1994), with 2 observations in Virginia of 9 eggs and 66 eggs, respectively. Our study identified multiple communal nest sites in both Alligator nests and Muskrat houses. One of our communal locations—the drone nest with a minimum of 932 Skink eggs/hatched eggshells—far exceeded previous reports; we believe numerous additional eggs and/or eggshells were likely overlooked. This Alligator nest (Fig. 5) appeared to be typical of those found in coastal marsh habitat, and we did not note any landscape features making it particularly attractive to Skinks for egg deposition. Assuming a maximum of 5 clutches per female annually (Fitch and Greene 1965) and a maximum 7 eggs per clutch, we calculated that a minimum of 27 female Skinks deposited the 932 known eggs and hatched eggshells found at this communal nesting site. Using a more conservative estimate of 3 eggs per clutch and 4 clutches per female over the summer, it is possible that up to 78 female Skinks may have used this site. Laboratory incubation study Our clutch-size estimates (1 to 5 eggs) concur with others from Louisiana (Arny 1948, Johnson 1953). In other parts of their range, Skink clutch sizes ranged from 1 to 7 eggs; the most frequent clutch size was 2–3 eggs (Cook 1943, Fitch and Greene 1965, Gibbons et al. 2009, Palmer and Braswell 1995). In 34 cases, we believe the Skink eggs/eggshells found possibly represented a single clutch, although we cannot rule out that 2 small clutches may have been deposited within a day or two Figure 5. First site visit to the Alligator nest in the field that eventually contained 932 Skink eggs/eggshells. In the photo, the nest has been opened to expose the Alligator eggs in the nest cavity, and the initial 42 Skink eggs collected are being held by inv estigator. Southeastern Naturalist 665 R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 of each other. If we assume these were cases of single use by 1 female depositing a clutch, there were several clutches containing 7 eggs—the maximum reported clutch size (Fitch and Greene 1965). Other researchers have reported egg dimensions similar to our findings, but without a known stage of incubation (Mitchell 1994, Palmer and Braswell 1995). Some egg measurements reported by Mitchell (1994) were larger than ours; it is unknown if egg size varies throughout the geographic range. Our results show that Skink eggs increased in length and width throughout incubation from approximately 8.6 mm x 5.4 mm at collection to 10.4 mm x 7.6 mm just prior to hatching, although we did not know the exact deposition date for eggs collected in the field. Lewis (1951) also reported an increase in egg dimensions during incubation for a single clutch. We could not calculate incubation periods for clutches collected in the field because we did not know the dates of egg deposition. However, our longest incubation period was ~1 month, corroborating estimates of incubation periods by others (Fitch and Greene 1965, Johnson 1953, Lewis 1951). We recorded hatchling sizes similar to those reported by others (Arny 1948, Davis 1945, Johnson 1953, Palmer and Braswell 1995). The absence of adult females at our nest sites (except possibly 2, observed on 1 occasion) indicated that females do not tend eggs after oviposition, which corroborates observations by Gibbons et al. (2009) and Mi tchell (1994). Benefits of commensal nesting Our study indicates the importance of both Alligators and Muskrats to Skinks for nesting in coastal marsh habitats. We did not observe nesting by other lizard species, though Green Anoles have been documented nesting in Alligator nests, albeit uncommonly (Brandt and Mazzotti 2000, Deitz and Jackson 1979, Kushlan and Kushlan 1980a). We also observed snakes nesting in Alligator nests, suggesting that these sites may also help to support populations of other herpetofauna in coastal marsh habitats. Alligator nests and Muskrat houses may become especially important during years when water levels are high, rendering marsh-grass clumps or other potential nesting sites unsuitable; Enge et al. (2000) hypothesized that variation in turtle use of Alligator nests may have been due to differences in waterlevel fluctuations or availability of alternative nesting sites. Water levels within the study site ranged from 0.30–0.63 m, well above marsh elevation (~0.24 m) during the June and July peak nesting period (D. Richard, LDWF, Grand Chenier, LA, unpubl. data). It is possible that Skink use of Alligator nests and Muskrat houses is reduced during normal water-level or drought years. Communal nesting also provides strategic advantages to numerous taxa (Doody et al. 2009, Radder and Shine 2007). Species that nest commensally in Alligator nests may benefit by the presence of the female Alligator deterring predators such as raccoons (Enge et al. 2000; Hall and Meier 1993; Kushlan and Kushlan 1980a, b). However, similar to Enge et al. (2000), we found a higher frequency of Skink nesting in inactive than active Alligator nests, and a high use of Muskrat houses, suggesting that the presence of female Alligators guarding nests does not confer a Southeastern Naturalist R.M. Elsey, M. Miller, D. LeJeune, and W. Selman 2016 Vol. 15, No. 4 666 reproductive advantage. Instead, our results suggest that Skinks use Alligator nests primarily because they provide suitable nesting habitat (large mounds of vegetation/ humus above water-level) and not because female Alligators are present. A recent paper documenting herpetofaunal diversity in a nearby (~17 km away) remnant coastal chenier forest (Selman 2015) documented capture of Little Brown Skinks, Plestiodon fasciatus L. (Common Five-Lined Skinks), and Northern Green Anoles. Interestingly, we did not document use of either Alligator nests nor Muskrat houses by the later 2 species. It is unclear why our current study (as well as past experience/observations) documented a far lower use of Alligator nests by turtles than has been reported in studies conducted in Florida (Enge et al. 2000). It may be that habitat differences (coastal marshes vs. lake habitat) may be a factor affecting turtle nest-site selection. However, to our knowledge there is no data documenting the species diversity, abundance, or nesting sites of turtles within the Superior marsh system. In summary, Skinks commonly use Alligator nests and Muskrat houses for nesting in coastal Louisiana; multiple female Skinks use these structures for nest sites, sometimes repeatedly in a season. It would be of interest to determine if other herpetofauna occupying nearby coastal chenier habitats might use either Alligator nests or Muskrat houses for egg deposition in this geographic region. 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