Spatial Ecology of the Eastern Massasauga (Sistrurus c. catenatus) in a New York Peatland

Society for the Study of Amphibians and Reptiles

Spatial Ecology of the Eastern Massasauga (Sistrurus c. catenatus) in a New York PeatlandAuthor(s): Glenn JohnsonSource: Journal of Herpetology, Vol. 34, No. 2 (Jun., 2000), pp. 186-192Published by: Society for the Study of Amphibians and ReptilesStable URL: http://www.jstor.org/stable/1565414 .

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Journal of Herpetology, Vol. 34, No. 2, pp. 186-192, 2000 Copyright 2000 Society for the Study of Amphibians and Reptiles

Spatial Ecology of the Eastern Massasauga (Sistrurus c. catenatus) in a New York Peatland

GLENN JOHNSON

Department of Biology, State University of New York at Potsdam, Potsdam, New York 13676, USA E-mail: [email protected]

ABSTRACT.- The eastern massasauga (Sistrurus catenatus catenatus) is listed as endangered in New York and is currently known from only two locations in the state. Characteristics of this species' spatial ecology and habitat preferences were investigated between 1989 and 1992 in Cicero Swamp, a large wetland complex near Syracuse, New York, which contains a 37 ha peatland of critical importance to massasaugas. Radiote- lemetered male (N = 11) and nongravid females (N = 2) left the peatland for nearby swamp forest soon after spring emergence while gravid females (N = 2) remained in the peatland until parturition. All telemetered snakes overwintered in the peatland. Of individuals tracked for the entire active season, gravid females moved significantly shorter distances per day (i = 7.1 m) and per season (i = 751.9 m) than either males (mean distance/day = 20.5 m; mean distance/season = 2940.2 m) or nongravid females (mean distance/ day = 22.9 m; mean distance/season = 3712.2 m). Similarly, 100% minimum convex polygon activity range estimates were smaller for gravid females (x = 2.0 ha) than for either males (x = 27.8 ha) or nongravid females (x = 41.4 ha). These findings suggest that conservation efforts for eastern massasaugas in Cicero swamp should focus on peatland habitat used by gravid females.

The spatial arrangement and movements of a mobile animal species clearly will reflect aspects of its behavior and ecology. Detailed knowledge of this information is critical to managers of wildlife resources, especially if the species in question is considered endangered, is regionally rare, or occurs on the periphery of its range in marginal habitat. Differences in activity patterns may exist between subgroups of a population, defined by size, age, sex, or reproductive condition, that will potentially impact conservation plans (Gibbons and Semlitsch, 1987). Addition- ally, there may exist seasonal or yearly differences in movement patterns, related to important life-history events, that need be determined (Gregory et al., 1987).

Advances in radio telemetry have made the study of the spatial ecology of generally secretive or inconspicuous organisms like snakes possible and evidence of intrapopulation differences is becoming apparent in many species (Gregory et al., 1987; Reinert, 1993). The eastern massasauga (Sistrurus c. catenatus), a wetland as- sociate across its range (Wright, 1941; Reinert and Kodrich, 1982; Seigel, 1986; Weatherhead and Prior, 1992), is at the easternmost point of its distribution in central New York. Here, as well as across its entire range, it is threatened with extinction and exists as relatively small and isolated relict populations (Beltz, 1993; Johnson and Breisch, 1993).

The specific objectives of this study were to determine the activity range and movement patterns of eastern massasaugas by sex and reproductive condition in Cicero Swamp, near Syra-

cuse, New York to (1) aid in the development of a management strategy for this species in the state and (2) compare results with telemetric studies of this species in other habitat types and geographic locations (i.e., wet prairie in western Pennsylvania, Reinert and Kodrich, 1982; conif- erous forest/wetlands in Ontario, Weatherhead and Prior, 1992).

MATERIALS AND METHODS

Study Area.-This study was conducted in the 2204 ha Cicero Swamp Wildlife Management Area (CSWMA) in Onondaga County, New York, 15 km northeast of Syracuse. CSWMA is owned and managed by the New York State De- partment of Environmental Conservation (NYS- DEC). CSWMA consists mostly of forested wetlands dominated by red maple (Acer rubrum). A 37 ha, weakly minerotrophic, shrub-dominated peatland that occurs near the western periphery of CSWMA is especially important to the CSWMA massasauga population, primarily for overwintering and gestation (Johnson, 1995). The composition and structure of the vegetation in this peatland are distinct from surrounding swamp habitat types, both on the ground and from examination of aerial photographs. The vegetation developed following an intense fire that occurred from June 1892 until the following January, consuming up to 1 m of peat (LeBlanc and Leopold, 1992). This area will be hereafter referred to as the "Burn Area". The ground vegetation layer here is composed of approximately 50% bryophytes (Sphagnum spp. and Polytrichum spp.). The dominant shrub species are moun-



MASSASAUGA SPATIAL ECOLOGY

tain-holly (Nemopanthus mucronata), highbush blueberry (Vaccinium corymbosum), and black chokeberry (Aronia melanocarpa). The general height of the shrub canopy is 1.5 to 2.0 m. Tree species include black spruce (Picea mariana), tamarack (Larix laricina) and red maple. A more detailed description of CSWMA is presented in LeBlanc and Leopold (1992) and Johnson and Leopold (1998). Nomenclature follows Mitchell (1986) for all vascular plant species.

Field and Telemetric Methods.-I located massasaugas by systematic searches in appropriate habitat at CSWMA over the period 1989-1993. Each captured individual was weighed, mea- sured, and given an individual mark by clipping the right or left half of one or two ventral scales (Brown and Parker, 1976a). Snakes were sexed by probing the cloaca for hemipenial pockets (Schaefer, 1934) and female snakes were palpated to determine reproductive status.

A subset of massasaugas captured at CSWMA was taken from the field for intraper- itoneal implantation of radiotransmitters using a modification of the methodology of Reinert and Cundall (1982). The major modifications were the use of the inhalant anesthetic methoxyflurane in place of halothane (Aird, 1986) and the mode of delivery of the anesthetic. Anesthe- sia was administered via a plastic cone placed over one end of a clear plastic tube containing the snake where rates of delivery and relative proportion of the anesthetic and oxygen could be monitored and adjusted. I used AVM model SM-1? and Holohil Systems Ltd. model SI-2T? transmitters. The greatest weight of any transmitter implant package used was 10.5 g and represented less than 5% of the body weight of a radio-implanted snake (Reinert, 1992). To reduce potential behavioral changes due to im-

plant mass, transmitters were implanted only in snakes greater than 250 g.

Snakes were released at the point of capture two days following surgery. Snakes were relo- cated approximately once every 48 h. At each radio-tracking location, I recorded the distance and bearing to the previous location. Movement distances are minimum estimates because snakes were assumed to have moved in a straight line between successive locations.

Analytical Methods-Between 10 August and 21 September 1993, the capture location, overwintering location, and other significant locations (birth sites, position following a move of a relatively long distance in a short time span) for each of the telemetered snakes monitored since 1989 were determined with a Magellan Systems Corporation NAV-5000 PRO? Global Positioning System (GPS) receiver. Data from the receiver were post-processed against an Ashtech Ranger base station receiver, using Ma-

gellan version 2.8 software, to obtain accuracies of 2-5 m for each located point. GPS data were prepared by J. Ozard and S. Crocoll (Habitat In- ventory Unit, NYSDEC).

I converted the distance to and bearing (polar coordinates) of each position to Universal Transverse Mercator (UTM) Cartesian coordinates. These UTM coordinates were loaded into the program HOME RANGE (Ackerman et al., 1989) to determine estimates of each individual's annual movements and activity range. I calculated activity range size using the minimum convex polygon method (Jennrich and Turner, 1969) and the harmonic mean method (Dixon and Chapman, 1980). The convex polygon method results are reported to facilitate comparisons with other studies that use this method (Ma- cartney et al., 1988). The harmonic means are also reported because they produce an estimate that is influenced by the distributions of radio locations and can identify multiple core areas (Tiebout and Cary, 1987; Reinert, 1992). How- ever all calculated activity ranges may enclose areas that were never visited by individual snakes. Using these methods, the 100% convex polygon and the 95% harmonic mean isopleth represent the total activity range and the 50% convex polygon and the 50% harmonic mean isopleth represent the core area (Tiebout and Cary, 1987; White and Garrott, 1990). The 50% convex polygons were determined by removing the furthest point from the geometric mean of all locations, then recalculating the geometric mean and removing the furthest point from the remaining locations and repeating until 50% of the locations are removed (Ackerman et al., 1989).

I performed a time series analysis (Reinert and Zappalorti, 1988; Reinert, 1992) to detect shifts in activity over time on individuals tracked at least 90 d. Location data for these individuals were grouped into 30-40 d intervals and the 100% convex polygon was calculated to determine time series activity ranges. I used the summed areas (minus overlap) per active season from the time series analysis to compare with the total season activity ranges. These are more realistic estimates of actual activity range than single estimates from the entire season's movements.

I used one-way ANOVA (a = 0.05) to test for differences in movement measures and activity range between males, nongravid females and gravid females. I used paired t-tests to investi- gate differences between 100% convex polygon and summed time-series activity range. I used the Pearson product-moment correlation to test for correlation between snout-vent length (SVL) and total distance moved, mean distance moved per day and, for individuals tracked for at least

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GLENN JOHNSON

TABLE 1. Means (SE) of movement measures for male, nongravid female, gravid female and all classes combined for Sistrurus c. catenatus in CSWMA monitored for a minimum of 95 days. Different letters in a column indicate significant differences from one-way ANOVA (P = 0.05) with LSD tests. Proportion of observations in which an individual moved -5 m.

Frequency Total distance Distance Range of movement1 moved moved/ day length

Group (%) (m) (m) (m)

Male 72.2A 2940.2A 20.5A 812.6A (N = 11) (3.21) (358.42) (2.25) (65.94)

Female, nongravid 74.0A 3712.2A 26.9A 1212.4B (N = 2) (8.00) (490.57) (2.69) (110.17)

Female, gravid 45.5B 751.9B 7.1B 295.6 (N = 2) (9.50) (186.34) (2.75) (98.75)

Total 68.9 2751.3 19.5 797.0 (N = 15) (3.59) (344.46) (2.20) (80.85)

100 d, activity range size (100% and 50% convex polygons). Due to their limited movements, gravid females were excluded from these correlation analyses.

RESULTS

Between 1989 and 1992, a total of 1097 observations for 15 monitored snakes was obtained. Some individuals were tracked for multiple years (two years, N = 6; three years, N = 3), although only three snakes were tracked for two complete seasons. Subsequent to spring emergence, the general movement pattern for male and nongravid female massasaugas was to leave the relatively open Burn Area and move into the surrounding swamp forest and uplands. The movement was typically preceded by a period of 10-20 d of relative inactivity near the overwintering location. Gravid females remained with their newborn offspring for several days and remained in the Bur Area until 10-12 d following parturition, at which time they moved beyond the borders of the Burn Area. This pattern observed in telemetered individuals supports field observations of non-telemetered gravid females. Core areas of gravid females were entirely within the Burn Area.

Differences were detected between sex and reproductive condition for mean frequency of movements (F2z2 = 5.27, P = 0.02) (Table 1) with gravid females making fewer movements (45.5% of the observations). No differences were detected between male and nongravid female massasaugas, possibly a result of low sample sizes. Similarly, differences were found in mean distance moved per day (F2,12 = 4.34, P = 0.04) and mean distance moved per season (F212 = 4.18, P = 0.04) with gravid females making shorter movements than either males and nongravid females. No differences were detected between male and nongravid female massasaugas for these parameters, although some indi-

vidual male snakes made extensive, but episod- ic, long movements (four instances of >1 km straight-line distance in two days). Range length differed among all three classes (F2,2 = 9.77, P = 0.003). Nongravid females showed the greatest mean range length (1212.4 m), followed by males (812.6 m), and gravid females (295.6 m).

Mean 100% convex polygons for all massasaugas monitored in CSWMA was 26.2 ha, whereas the mean 95% harmonic mean isopleth was 44.3 (SE + 7.409) ha. Convex polygon estimates averaged 60% of harmonic mean estimates and were significantly positively correlated with the latter (r = 0.90, P < 0.01). Similarly, the mean 50% harmonic mean isopleth was greater than the 50% convex polygon (9.91 + 1.93 vs. 5.2 ? 1.15) and the two were positively correlated (r = 0.69, P < 0.01).

There were significant differences among sex and reproductive condition groups (F2,2 = 3.88, P = 0.05) with gravid females utilizing smaller activity ranges than males or nongravid females (Table 2.). These latter two groups did not differ significantly. No significant differences were detected in core areas among the three groups (F,,12 = 1.98, P = 0.18).

The total area of these seasonal ranges for 15 individuals averaged 53.1 ? 3.5% of the 100% convex polygon activity range. Gravid females seasonal ranges covered a greater percentage of the total range (x = 78 ? 4.98, F212 = 11.22, P < 0.01) than was the case for males (x = 51.1 ? 2.76) or nongravid females (x = 39.11 + 2.17).

No significant correlations were detected between SVL and frequency of movement (r = 0.02, P = 0.944), mean distance moved per day (r = 0.14, P = 0.643), total distance moved (r = 0.04, P = 0.885), range length (r = 0.37, P =

0.212), 100% activity area (r = 0.06, P = 0.850) or 50% activity area (r = -0.11, P = 0.728) among male and nongravid female snakes combined. Male snakes tested alone also showed no

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TABLE 2. Means (SE) of activity range measures for male, nongravid female, gravid female and all classes combined Sistrurus c. catenatus in CSWMA monitored for a minimum of 95 days. Different letters in a column indicate significant differences from one-way ANOVA (P = 0.05) with LSD tests.

50% 100% minimum minimum Sum of seasonal % sum of Harmonic mean convex polygon convex 100% polygons seasonal ranges

Group (ha) polygon (ha) (ha) of total range 95% isopleth 50% isopleth

Male 27.8A 6.3A 14.75A 51.11A 46.1A 11.5A (N = 11) (4.81) (1.33) (3.02) (2.76) (7.67) (2.27)

Female, nongravid 41.4A 4.3A 16.25A 39.11A 71.1A 10.8A (N = 2) (3.36) (2.36) (2.21) (2.17) (20.09) (1.47)

Female, gravid 2.OB 0.1A 1.62A 78.02B 7.1B 0.4A

(N = 2) (0.83) (0.03) (0.78) (4.99) (2.76) (0.18) Total 26.2 5.2 13.20 53.10 44.3 9.91

(N = 15) (4.49) (1.15) (2.52) (3.50) (7.41) (1.93)

significant correlations for these measures. There was a significant positive correlation among male snakes between number of days tracked and total distance moved (r = 0.56, P =

0.024), although 100% activity ranges were not correlated with number of days tracked (r = 0.26, P = 0.395). Sample sizes for females were judged too small for a similar analysis.

Three snakes were tracked for two complete successive seasons. Male snake 2.27 and male snake 1.3 showed little difference in 100% minimum convex polygon activity range size between years, however male snake 3.2 used an activity range more than twice the size in 1991 (41.4 ha) than in 1990 (17.8 ha). There was considerable overlap of total activity range by individual snakes between years although core areas between years never overlapped.

DISCUSSION Gravid females, telemetered or not, were nev-

er encountered outside the Burn Area over the course of the study. All three telemetered snakes had small activity ranges and restricted movements, generally in the vicinity of their previous winter's hibernation location. The total size of their activity ranges was increased by brief, but extensive, movements following parturition. Gravid females of several snake species have been shown to exhibit smaller movement indices than males and nongravid females, in- cluding Crotalus horridus (Reinert and Zappalor- ti, 1988), C. cerastes (Secor, 1994), Agkistrodon contortrix (Fitch and Shirer, 1971), Pseudechis porphyriacus (Shine, 1987), Viper berus (Vitanen, 1967), and Coluber constrictor (Brown and Parker, 1976b).

There is little evidence of territorial behavior or intraspecific mutually exclusive activity ranges in snakes (Gregory et al., 1987; Macartney et al., 1988). Instead, many snake species show overlapping activity ranges among individuals (Viitanen, 1967; Wharton, 1969; Brown and

Parker, 1976b; Madsen, 1984; Macartney et al., 1988). Limitations in such resources as food, summer refugia, oviposition sites, and overwintering sites have been proposed to explain this apparent lack of territoriality (Gregory, 1982; Duvall et al., 1985; Weatherhead and Hoysak, 1989; Secor, 1994). Reinert and Kodrich (1982) suggested that the specific habitat requirements of gravid massasaugas accounted for a detected overlap in activity range. In CSWMA, overlapping core areas among snakes are probably related to the concentration of hibernation and gestation sites within the Burn Area and the generally widely spaced foraging opportunities found in the surrounding swamp forest.

Male snakes continue to move throughout the active season; however no expansion of activity range occurred with increasing days tracked beyond 100 d. This supports field observations that suggest male massasaugas are making a re- turn movement toward the Burn Area at some critical point in the active season. One possible explanation is that males are moving closer to the Burn Area to increase their chances of en- countering female massasaugas. Field observations indicate that courtship and mating occur in August-September at CSWMA and most of these observations were near the periphery, but not within, the Burn Area. Alternatively, male snakes could be simply returning to the vicinity of their hibernation sites in preparation for overwintering.

Two telemetric studies have previously been published on eastern massasauga movements and activity patterns. Reinert and Kodrich (1982) studied massasaugas in two disjunct sites in western Pennsylvania. These sites more close- ly resemble massasauga habitats in wet prairie ecosystems (Maple and Orr, 1968; Bielema, 1973; Seigel, 1986) in the midwestern United States. Nearly all the activity at these sites occurred in open vegetational communities with

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GLENN JOHNSON

TABLE 3. Means of movement and activity measures for Sistrurus c. catenatus, in three locations across its

range (western Pennsylvania-Reinert and Kodrich 1982; Bruce Peninsula-Weatherhead and Prior 1992; Cicero Swamp-this study).

Frequency Total distance Distance Range 100 minimum of movement moved moved / day length convex polygon

Location (%) (m) (m) (m) (ha)

Bruce Peninsula Ontario (N = 11) 67.1 1823.6 56.0 1030.4 25.0 Western Pennsylvania (N = 25) -9.1 89.0 1.0 Cicero Swamp New York (N = 15) 68.9 2751.3 19.5 797.0 26.2

little movement into surrounding forest. Move- ments and activity ranges were considerably smaller at these Pennsylvania sites than at CSWMA (Table 3). These authors also noted no differences between gravid females and other snake groups in all movement measures except range length. There are several explanations for these differences observed between CSWMA and the Pennsylvania locations. First, Reinert and Kodrich's snakes were force-fed transmitters and this may reduce movements by induc- ing thermophily or simulating meals (Reinert and Cundall, 1982; Lutterschmidt and Reinert, 1990). Second, individuals in this study were tracked for relatively short periods and never for a complete active season. Gravid snakes may have moved less often over smaller ranges than other members of the population at the Penn- sylvania sites. Finally, and most convincing, is that all life requisites may be met within the meadow and old field habitats of western Penn- sylvania. Massasaugas hibernate in crayfish (Cambarus spp.) burrows that occur in these open habitats where basking opportunities abound. Small mammals, the primary prey of

massasaugas (Keenlyne and Beer, 1973; Seigel, 1986) are low in abundance in the Bum Area (Johnson, 1995). Peatlands typically support a lower abundance and diversity of small mammals than upland habitats (Nordquist, 1992). Fi-

nally, more recent observations (D. Johnson, pers. comm.) indicate that massasaugas may uti- lize forested habitat at one of the Pennsylvania sites.

The other previous study was conducted largely within the Bruce Peninsula National Park (BPNP) in Ontario, which contains a relatively large, disjunct population of eastern massasaugas near the northern extent of their range (Weatherhead and Prior, 1992). Activity ranges of massasaugas there were nearly identical to those in this study (Table 3). Massasaugas in BPNP moved more than twice as far per day, but moved significantly smaller total distances. This may be partly explained by the shorter tracking periods (x = 36.5 d) in the Ontario study. Females in the Ontario study reportedly had significantly smaller activity ranges and

other movement indices than males; however, it was unknown or unclear if any of the females were gravid. Gravid snakes in the Ontario study population would most likely influence conclu- sions about sex differences and movement. Mean range length was substantially longer in the Ontario population suggesting the shape of the activity polygons at BPNP may have been more elongate than those at CSWMA. Snakes at BPNP showed a clear association with conifer- ous forest openings and wetlands in summer, fall, and at hibernation and an avoidance of open areas and other forest types. Wetlands composed only a small percentage of available habitat at BPNP.

Caution must be used when interpreting information drawn from small sample sizes, such as the female populations reported here. Some non-significant differences shown in Table 2 could be the result of small sample sizes. Due, in part, to size constraints imposed by the transmitter package and to a relatively small population of secretive snakes, movement measures obtained for this population of massasaugas were restricted to larger adult animals. Very little is known about neonate and subadult massasaugas at CSWMA, population classes that may suffer the greatest risk of mortality (Scott and Seigel, 1993). Neonates and small massasaugas were never encountered outside the Burn Area; however, they may very well travel into adjacent habitats. Recent evidence from radi- omarked neonate massasaugas in Wisconsin suggests they may move considerable distances over the period between birth and hibernation (R. King, pers. comm.).

The results of this study indicate that the peatland habitat is critical for the survival of the eastern massasauga in CSWMA, and its primary value lies in containing the majority of suitable overwintering sites for all members of the population as well as primary gestation sites for gravid females. Prior to this study, it was believed that most massasaugas in CSWMA remained in the Burn Area throughout the active season (Johnson and Breisch, 1993) and presum- ably met all their life requisites there. Based upon observed movement patterns in this study,

190




males, nongravid females, and postpartum females left this habitat, possibly for more prof- itable foraging opportunities in surrounding forest. This pattern of movement suggests that (1) management activities need to focus on the juxtaposition of several habitat types, especially where critical overwintering areas, such as the peatland in CSWMA, support low small mam- mal populations and (2) at CSWMA, habitat management should focus on the life requisites of gravid females (Johnson and Leopold, 1998).

Acknowledgments.-I thank A. R. Breisch of the NYS Department of Environmental Conserva- tion for initially suggesting and providing materials and advice for this study and Dr. C. Wal- lace, veterinarian at the Burnet Park Zoo, for transmitter implantation. M. Morrison, T. Sin- ander, M. E Ingraldi, R. W. Baker, W. E. Burns, M. S. Keefe, K. Anderson, T. C. Wills, D. R. Hampton, K. K. Brewer, E. A. Balko, S. L. Doran and M. A. Connerton assisted with radiotrack- ing. Funding was provided by The American Wildlife Research Foundation, SSAR Grants-in- Aid of Research, Upstate Herpetological Society, and the Research Foundation of the SUNY Col- lege of Environmental Science and Forestry. H. K. Reinert, D. J. Leopold, A. R. Breisch, and K. A. Prior provided constructive criticism of ear- lier versions of this paper.

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GLENN JOHNSON GLENN JOHNSON

gel and J. T. Collins (eds.), Snakes: Ecology and Behavior, pp. 201-240. McGraw-Hill Inc., New York.

, AND D. CUNDALL. 1982. An improved surgical implantation method for radio-tracking snakes.

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SCHAEFER, W. H. 1934. Diagnosis of sex in snakes. Copeia 1934:181.

SCOTT, N. J. JR., AND R. A. SEIGEL. 1993. The management of amphibian and reptile populations: species priorities and methodological and theoretical constraints. In D. R. McCullough and R. H. Barrett (eds.), Wildlife 2001:Populations, pp. 343-368. El- sevier Applied Science, New York.

SECOR, S. M. 1994. Ecological significance of movements and activity range for the sidewinder, Cro- talus cerastes. Copeia 1994:631-645.

SEIGEL, R. A. 1986. Ecology and conservation of an

endangered rattlesnake, Sistrurus catenatus, in Mis- souri, USA. Biol. Conserv. 35:333-346.

SHINE, R. 1987. Intraspecific variation in thermoregu-

gel and J. T. Collins (eds.), Snakes: Ecology and Behavior, pp. 201-240. McGraw-Hill Inc., New York.

, AND D. CUNDALL. 1982. An improved surgical implantation method for radio-tracking snakes.

Copeia 1982:702-705. , AND W. R. KODRICH. 1982. Movements and

habitat utilization by the massasauga, Sistrurus catenatus catenatus. J. Herpetol. 16:162-171.

, AND R. T. ZAPPALORTI. 1988. The timber rattlesnake (Crotalus horridus) of the Pine Barrens: its movement patterns and habitat preference. Copeia 1988:964-978.

SCHAEFER, W. H. 1934. Diagnosis of sex in snakes. Copeia 1934:181.

SCOTT, N. J. JR., AND R. A. SEIGEL. 1993. The management of amphibian and reptile populations: species priorities and methodological and theoretical constraints. In D. R. McCullough and R. H. Barrett (eds.), Wildlife 2001:Populations, pp. 343-368. El- sevier Applied Science, New York.

SECOR, S. M. 1994. Ecological significance of movements and activity range for the sidewinder, Cro- talus cerastes. Copeia 1994:631-645.

SEIGEL, R. A. 1986. Ecology and conservation of an

endangered rattlesnake, Sistrurus catenatus, in Mis- souri, USA. Biol. Conserv. 35:333-346.

SHINE, R. 1987. Intraspecific variation in thermoregu-

lation, movements and habitat use by Australian blacksnakes Psuedechis porphyriacus (Elapidae). J. Herpetol. 21:165-177.

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WRIGHT, B. A. 1941. Habit and habitat studies of the massasauga rattlesnake (Sistrurus catenatus catenatus Raf.) in northeastern Illinois. Amer. Midl. Na- tur. 25:659-672.

Accepted: 10 January 2000.

lation, movements and habitat use by Australian blacksnakes Psuedechis porphyriacus (Elapidae). J. Herpetol. 21:165-177.

TIEBOUT, H. M., AND J. R. CAREY. 1987. Dynamic spatial ecology of the water snake, Nerodia sipedon. Copeia 1987:1-18.

VIITANEN, P. 1967. Hibernation and seasonal movements of the viper, Viper berus (L.), in southern Fin- land. Ann. Zool. Fennici. 4:472-546.

WEATHERHEAD, P. J., AND D. J. HOYSAK. 1989. Spatial and activity patterns of black rat snakes (Elaphe ob- soleta) from radiotelemetry and recapture data. Can. J. Zool. 67:463-468.

, AND K. A. PRIOR. 1992. Preliminary observations of habitat use and movements of the eastern massasauga rattlesnake (Sistrurus c. catenatus). J. Herpetol. 26:447-452.

WHARTON, C. H. 1969. The cottonmouth moccasin on Sea Horse Key, Florida. Bull. Florida State Mus. Biol. Sci. 14:227-272.

WHITE, G. C., AND R. A. GARROTT. 1990. Analysis of Wildlife Radio-Tracking Data. Academic Press, San Diego.

WRIGHT, B. A. 1941. Habit and habitat studies of the massasauga rattlesnake (Sistrurus catenatus catenatus Raf.) in northeastern Illinois. Amer. Midl. Na- tur. 25:659-672.

Accepted: 10 January 2000.


Does Foraging Activity Change with Ontogeny? An Assessment for Six Sympatric Species of Postmetamorphic Litter Anurans in

Central Amazonia

ALBERTINA P. LIMA AND WILLIAM E. MAGNUSSON

Coordenacao de Pesquisas em Ecologia, Instituto Nacional de Pesquisa da Amazonia, CP 478, 69011-970 Manaus AM, Brasil. E-mail: [email protected]

ABSTRACT.-We studied the foraging activities of six frog species in their natural habitat, the leaf litter of tropical rain forest in central Amazonia. To describe intraspecific ontogenetic change in general activity during foraging, we used four indices of general activity (movement frequency, velocity when moving, time

spent moving, and total distance moved). The association between each of the four indices and the size of

frogs varied among species. The indices of foraging activity do not represent independent information. Therefore, we reduced the dimensionality using a single ordination obtained by multidimensional scaling, and investigated its relationship to frog size and type and size of prey. There was a significant relationship between the combined index of foraging activity and frog size in three of the six species. Foraging activity predicted the intraspecific change in the type and size of prey for Eleutherodactylus fenestratus, partially for Adenomera andreae, Epipedobates femoralis, and Dendrophryniscus minutus, and not for Bufo cf. typhonius and Colostethus marchesianus.


Does Foraging Activity Change with Ontogeny? An Assessment for Six Sympatric Species of Postmetamorphic Litter Anurans in

Central Amazonia

ALBERTINA P. LIMA AND WILLIAM E. MAGNUSSON

Coordenacao de Pesquisas em Ecologia, Instituto Nacional de Pesquisa da Amazonia, CP 478, 69011-970 Manaus AM, Brasil. E-mail: [email protected]

ABSTRACT.-We studied the foraging activities of six frog species in their natural habitat, the leaf litter of tropical rain forest in central Amazonia. To describe intraspecific ontogenetic change in general activity during foraging, we used four indices of general activity (movement frequency, velocity when moving, time

spent moving, and total distance moved). The association between each of the four indices and the size of

frogs varied among species. The indices of foraging activity do not represent independent information. Therefore, we reduced the dimensionality using a single ordination obtained by multidimensional scaling, and investigated its relationship to frog size and type and size of prey. There was a significant relationship between the combined index of foraging activity and frog size in three of the six species. Foraging activity predicted the intraspecific change in the type and size of prey for Eleutherodactylus fenestratus, partially for Adenomera andreae, Epipedobates femoralis, and Dendrophryniscus minutus, and not for Bufo cf. typhonius and Colostethus marchesianus.

There is evidence that the composition of the diet of many amphibians and reptiles depends on how widely the species forages (Huey and Pianka, 1981; Magnusson et al., 1985; Toft, 1985;

There is evidence that the composition of the diet of many amphibians and reptiles depends on how widely the species forages (Huey and Pianka, 1981; Magnusson et al., 1985; Toft, 1985;

Wiggins, 1992). For species of leaf-litter frogs, Toft (1981) suggested that the mechanisms that determine the differences in size and type of prey are related to foraging mode. In general,

Wiggins, 1992). For species of leaf-litter frogs, Toft (1981) suggested that the mechanisms that determine the differences in size and type of prey are related to foraging mode. In general,

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Documents

Spatial Ecology of the Eastern Massasauga (Sistrurus c. catenatus) in a New York Peatland