TIMMERMAN: CROTALUSADAMANTEUS ON ORDWAY PRESERVE


years. The mean home range for these diamondbacks (minimum convex polygon)
was 73.5 ha (Table 1). Females averaged 46.5 ha, while males averaged 84.3 ha.
M3 exhibited a different-sized home range between years. In 1987 it used 75.7 ha
and in 1988 it used 166.2 ha, encompassing much of the previous year's range.
The smallest home range (25.7 ha) belonged to M4.
 It has been suggested that seasonal changes in habitat productivity may result
in changes in home range size (Harestad and Bunnell 1979). If this is true, it is
likely that the home range of C. adamanteus changes over time, fluctuating as the
home range of M3 did from 1987 to 1988. Sigmodon hispidus, one of the
diamondback's principal prey, becomes exceedingly rare during droughts (J.F.
Eisenberg unpubl. data), which are fairly common in north-central Florida..
Therefore, snakes may have to increase their home range size to find sufficient
food. The Ordway has experienced reduced rainfall over the past several years
(Franz and Dodd unpubl. data), but the historic rain patterns are unknown.
 Average home ranges for Ordway diamondbacks are somewhat smaller than
the ranges for Tall Timbers rattlesnakes (Means 1985). Tall Timbers females
ranged over about 80 ha compared to about 50 ha for Ordway females and males
used up to 200 ha compared to about 85 ha for Ordway males. However, we did
not use identical home-range analytical techniques (Means pers. comm.), so it is
not surprising that the values are somewhat different. Alternate methods of home-
range estimation can provide different results, even in the same data set. As an
example, using the minimum convex polygon method, which I have reported here,
the home range of Ml is about 54 ha. However, using the 95% ellipse method, the
same plotted coordinates yield a home range of 166 ha, an increase of 307% (see
Table 1). Based on other radio-telemetry studies at the Ordway Preserve, Florida
pine snakes (Franz 1984), eastern indigos, and eastern coachwhips (Dodd et al.
1988) have ranges that are similar in size to that of the eastern diamondback.
 Some rattlesnake home ranges overlapped (Fig. 1). In addition to the
radio-tagged snakes whose ranges are outlined in this figure, eight other
rattlesnakes were seen by field personnel in the areas used by telemetered snakes.
This evidence suggests that diamondback rattlesnakes are not territorial.

 Density.- No authoritative density estimates of C. adamanteus in native
habitats has ever been made. Nevertheless, a crude density estimate is possible
based on the observations of Ordway field personnel over the course of this study.
A total of ten adult rattlesnakes were observed in the area just northeast of Ross
Lake. Applying the average home range from this study, and drawing circular
ranges around their locations, it can be estimated that this aggregation was
occupying roughly 100 ha. We know that this sample does not represent 0% of the
population in that 100 ha, nor does it likely represent 100% of the population. If
we assume that it accounted for about 50%, we can derive a population of 20 adult
snakes. This results in a crude density estimate of 1 rattlesnake per 5 ha. If we