1 0 0
FIGURE 7-15.—Fidelity of Artibeus jamaicensis to the Chapman locality group on BCI. Frequency of capture of individual bats with records of multiple captures that were caught at least once at Chapman are graphed as percentages of records in various fractional capture categories ('/6 or less of records = 0%-19%, Vs-V*
= 20%-29%, V3 = 3O%-39%, 2/s = 40%-49%, lh = 50%-59%, Vs-Vi = 60%-69%, 3A = 70%-79%. 4/ s -
5/6 = 80%-99%, all = 100%). Row A in the table lists fractional capture categories (as percentages), row B lists number of individual bats whose records at Chapman fall into each category (n = 190), and in row C the numbers are converted to percentages. See also Table 7-7.
Fidelity
We examined fidelity to a particular locality group by analyzing suites of multiple capture records of individual bats.
For each locality group we compiled records of all A.
jamaicensis having multiple captures that were taken at least once in that particular locality group between October 1976 and October 1980. For each bat, we tabulated total captures, the number of captures in that particular locality group, and percentage of its total records in that locality group. From that tabulation we grouped those having multiple captures accord- ing to the percentage of their occurrence at that locality group among total records (e.g., Chapman, Figure 7-4).
The distribution of records among fractional categories is influenced by the number of records per individual suite. In all, 3846 A. jamaicensis were recaptured (Figure 7-14). Most (57%) were recaptured only once (i.e., had two captures), 24%
were recaptured twice (three captures), 11% recaptured three
times (four captures), and 8% recaptured four or more times.
Thus, peaks would be expected (Figure 7-15) at 50% and 100%
for two-record suites; 33%, 66%, and 100% for three records;
and 25%, 50%, 75%, and 100% for four records, and so forth.
Because most recaptured bats were caught again only once, 50% and 100% peaks per locality should occur most often.
These data indicate fidelity to a particular locality group.
High fidelity means a high frequency of records in the 60%-100% interval, which represents 3/s, 2/3,3A, 4/s, or more captures in the same area. The hiqher the frequency of same-site captures, the higher the fidelity. Low fidelity is revealed by a higher frequency of records in the 0%-40%
interval (2/s, lfr, !/4, Vs, and !/6 of captures or less) for that locality group. A simplified summary (Table 7-7) of locality- group fidelity, like that in Figure 7-15, shows three basic patterns among our data.
Pattern I (e.g., Armour End; Figure 7-16, Table 7-7) covers most of the locality groups. There is a strong similarity among
110 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
© — Ov O tn l^ oo vd
-^ co —
oo >n so so r-
f r~ ts oo >/•> oo
« N f /I -
- ^ ~ * SO —* CO ^^ CO ^^ — — co r- co
I g
NUMBER 511
60-
50
111
o cc
0.
<
o
CO
<
00
40-
30-
20-
10-
0
J"O = Chapman
• • • Conrad A - Fuertes
•A ' Orchid Island
0-19 20-29 30-39 40-49 50-59 60-69 70-79 80-99
CAPTURE CATEGORIES (%)
FIGURE 7-16.—Fidelity of Artibeus jamaicensis to Pattern I locality groups on and near BCI: Chapman, Conrad, Fuertes, and Orchid Island. See Figure 7-15 for further explanation.
1 0 0
the capture-category tabulations for locality groups with this pattern in spite of their diverse locations and the disparity in numbers in each suite of multiple capture records (from 51 to 1321). These locality groups share a low degree of fidelity (<19% in the 60%-100% column) and a high frequency of single captures (82%-99% in the 0%-40% and 0%-50%
columns).
Pattern II (Lutz, Bohio, and Standley End; Figure 7-17, Table 7-7) comprises three seemingly unrelated locality groups whose records of fidelity are remarkably similar. All three show higher fidelity, compared with the Pattern I locality groups (30%-32% in the 60%-l00% column), and fewer single records (68%-70% in the 0%-40% and 0%-50%
columns). Their records may be similar for different reasons.
We sampled little of the probable foraging range of the Bohio bats, so they had little risk of capture except at Bohio, thereby appearing to have high fidelity to that location. In contrast, the bats of Standley End may actually be sedentary because they were recaptured mostly at Standley End or nearby (see Figure 7-8 and discussion of Core Areas earlier in this section). Or, if
we sampled only part of their foraging areas, the situation at Standley End may be similar to that at Bohio.
We are confident that we have sampled the full extent of the foraging ranges of Lutz bats. High fidelity to Lutz may reflect a larger local resident population, or may result from catching the same individuals repeatedly because of the attraction of the fig grove in Lutz Ravine. These fig trees may adequately support local populations of A. jamaicensis and periodically attract bats from afar when ripe figs are scarce elsewhere. If this is true then some of the bats showing high fidelity are actually opportunistic transient foragers rather than Lutz residents.
Pattern III (Buena Vista and Pefia Blanca; Figure 7-18, Table 7-7) shows the highest fidelity. The obvious explanation for this pattern is that we sampled only a fraction of the foraging ranges of these bats, and because we captured them mostly at their day roosts. We netted bats only at night at all other locality groups and, evidently, we did not net where the bats of Buena Vista and Pefia Blanca most often foraged.
The degree of fidelity within patterns appears to be related to netting effort. On this basis we sorted Pattern I locality groups
112 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
50-|
40-
Q
c 30 -\
O
CD
20-
10-
0
JO = B oh i o
• = Standley End
• = Lutz
I | • • • • • •
0-19 20-29 30-39 40-49 50-59 60-69 70-79 80-99
CAPTURE CATEGORIES (%)
FIGURE 7-17.—Fidelity of Artibeus jamaicensis to Pattern II locality groups on and near BCI: Bohio, Lutz, and Standley End. See Figure 7-15 for further explanation.
1 0 0
into two subpatterns (Table 7-8). One with 19 or more netting-nights per locality (subpattern la); the other with fewer (subpattern Ib). With few exceptions (low fidelity at Conrad and Lake-Wheeler; unusually high fidelity at Drayton End), fidelity and netting effort within patterns are directly and positively correlated, suggesting that the more often a locality group is netted the more likely the bats using that locality group will be recaptured.
Nevertheless, although netting effort differed greatly be- tween subpatterns la and Ib, fidelity was similar. Therefore, variation in fidelity between patterns is independent of netting effort. Subpattern la localities were netted from 20 to 52 nights and fidelity ranged from 7% to 18% (Table 7-8). Subunit Ib localities were netted only 6 to 17 nights apiece, yet the fidelity range was similar (8%-16%).
Fidelity was surprisingly similar (30%-32%) among pattern II localities even though netting effort ranged from 14 nights at Bohio to 197 at Lutz (Table 7-7). However, when comparing fidelity on the basis of similar netting effort between patterns I and II the results are markedly different. For example, 14 netting nights demonstrated 6% and 14% fidelity in Pattern I, and 30% fidelity in Pattern II. Locality groups with 24 and 26 netting nights in Pattern I showed 9% and 13% fidelity;
whereas fidelity was more than double (31%) after similar effort at Standley End (25 netting nights) in Pattern II.
If all bats having multiple captures that were recaptured only once in a particular locality group are excluded, we should eliminate most that were probably based elsewhere. Following that logic, we considered A. jamaicensis captured two or more times in a locality group more likely to be local residents. The proportion of bats with two or more captures in a locality group to the total multiple-capture cohort from that locality group varied from 0.9% to 71.9%; although they still sorted into the same patterns I, II, and III (Table 7-7). Few individuals caught two or more times confirms low fidelity at locality groups such as Conrad (11%) and Chapman (18%). The two-plus capture fraction at Conrad may contain few local bats, judging from the lower proportion (54%) of those bats in the 60%-100%
column. However, the high percentage (78%) in the 60%- 100% fractional capture category at Chapman indicates that the two-plus fraction, although small, may represent mostly local bats. The high proportion (78%) of bats at Pefla Blanca that were caught there at least twice, and the high percentage (92%) of those in the 60%-100% bracket, suggest that this exercise is a valid means of estimating fidelity to a locality because high fidelity is to be expected at a harem day roost.
NUMBER 511
50
w 4 0 - Q
LU
cc 3 0
Q_
O 20 H
113
CO
CD
10-
0
JBuenavista Light Pena Blanca Light
I 1 1 1 " 1 1 • — i 1
0-19 20-29 30-39 40-49 50-59 60-69 70-79 80-99
CAPTURE CATEGORIES (%)
FIGURE 7-18.—Fidelity of Artibeus jamaicensis to Pattern III locality groups near BCI: Buena Vista and Pena Blanca. See Figure 7-15 for further explanation.
1 0 0
We found that 102 (37%) of the 275 A. jamaicensis caught at Standley End had been caught there at least twice (Table 7-7).
Of these, 83% fall into the 60%-100% recapture category for the site. This is good evidence that a high proportion of the Standley End bats were local residents, a conclusion further supported when we examine their records in greater detail.
Only two (7%) of the two-plus females were caught as many as two times elsewhere (at Bohio and Standley Ridge). Also, only six (8%) of the males caught two or more times at Standley End were caught as many as two times at other sites, all nearby (Fuertes, 1; Miller Ridge, 8; and Standley Ridge, 2).
The sex ratio of the Standley End A. jamaicensis (102) is skewed toward males (73 : 29; Table 7-9). At Lutz, another Pattern II locality with similar fidelity statistics, the ratio is 53 :47. During three of the netting episodes at Standley End when two-plus bats were caught, males outnumbered females 30 to 1. Of males caught at least twice, 31% were also caught three or more times while only 14% of the females were caught that often. In contrast, only 21 (29%) males were caught over a relatively long period (two to four years), whereas 14 (48%) females were recaptured at Standley End during the same period. Close to three-fourths (71%) of the males were found there for a year or less (Table 7-9). Age distribution among bats
captured two or more times was similar in males and females (Table 7-10); however, a larger proportion of the young males than young females stayed in the area to be caught later as adults.
We believe that the males at Standley End were predomi- nantly bachelors, and that most or all of the resident females were members of harems. Of the 20 females caught as adults during seasons of reproduction, 18 were pregnant, lactating, or postlactating at one or more of the captures. The greatest number of females caught as adults at Standley End in any half year was 11. Presuming that we caught most of the resident females, they probably represent from one to three harems. In the four harems of A. jamaicensis that Morrison (1979) studied on BCI, he found from four to 11 adult females (X= 6.5).
We still do not know why fidelity was so high in the three Pattern II locality groups (Lutz, Bohio, and Standley End).
Incomplete coverage of foraging ranges may be a factor at Bohio and Standley End, but not at Lutz, which is surrounded by well-netted localities that have typical low Pattern I fidelity percentages. Other peripheral locality groups such as Chapman, Standley Ridge, and Armour End show low fidelity, suggesting that peripheral location is not the reason.
114 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY TABLE 7-8.—Fidelity of Artibeus jamaicensis to a particular locality on BCI,
ranked by number of netting nights. See Table 7-7 and text for explanation of categories.
Locality
PATTERN la (more than 19 netting nights) Miller Ridge
Plateau Fuertes Shannon-AMNH Barbour-Hood
PATTERNIb (less than 19 netting nights) Chapman
Standley Ridge Barbour Stream Conrad Lake-Wheeler Harvard Armour End Drayton End Zetek21 Gross Point Shannon-Balboa Orchid Island
PATTERN II Lutz
Standley End Bohio
Rank
1 2 3 4 5
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3
Netting nights
52 46 26 24 20
17 16 14 14 12 11 11 10 6 5 4 4
197 25 14
60-100%
18 12 13 9 7
16 15 14 6 4 12 8 14 8 1 3 3
32 31 30
We suggest that the high capture rate at Lutz is correlated with the unusual local abundance of fig trees. That also could be true of Bohio because our netting there generally coincided with the availability of ripe figs; however, fig trees were scarce at Standley End. The abundance of fig trees at Miller Ridge rivals that of Lutz, yet fidelity was low, as was typical of other
Pattern I locality groups. Geographically, the Pattern II locality groups are dissimilar: Bohio is on the mainland, Standley End is peripheral on BCI, and Lutz is more central. In terms of size, Lutz encompasses the largest area, and because of its proximity to the Laboratory Clearing, it received the greatest sampling effort. Lacking a better explanation, one could argue that the similarities in capture frequency among the locality groups in Pattern II are merely coincidental.
Movements of Individual Bats
Thus far we have discussed movements of bats associated with a particular locality group based on pooled data. We also examined the movements of individuals captured at two or more localities away from the central locality under considera- tion. To illustrate this we have mapped the movements of five female A. jamaicensis from Pefia Blanca (Figure 7-19). Each female was caught at two or more localities away from the light tower, and polygons outlining the locations where each was captured approximate their known home ranges. We then overlaid this map (Figure 7-19) with a 0.5 km grid and counted the number of times individual polygons touched each square.
The resulting map (Figure 7-20) shows the frequency (from one to five) of occurrence of individual bats in each of the squares.
We also mapped the same kind of information from 11 bats of the day roost in the Buena Vista light tower (Figure 7-21).
This method proved effective for illustrating movements
TABLE 7-10.—Age distribution of Artibeus jamaicensis captured two or more times at Standley-End, BCI.
Sex
Female Male
Caught only when young
Caught first as young later as adult
Caught only as adult 14%
6%
38%
49% 45%
Sex
FEMALE number percent
MALE number percent
TABLE 7-9.—Sexual variation in age, or more times at Standley-End, BCI.
N J-S
29
73 1 1
Age during capture span J-A SAD
3 4 10 14
11 4 15 6
S-A
8 28
24 33
capture span, and number of captures of Artibeus jamaicensis caught two
AD
14 48
33 45
1
15 52
52 71
Capture span (years) 2 3
7 4 24 14 48%
13 7 18 10 29%
4
3 10
1 1
Number of captures at Standley-End 2
25 86
50 68
3 4 5+
3 1 10 4
14%
14 8 1 19 11 1
31%
2
11 38
31 42
Total captures 3
9 31
20 27
4
8 28
10 14
5
1 3
8 11
6+
4 5
NUMBER 511 115
4 5
i . • • • i . . . .
2 3 kilometers
FIGURE 7-19.—Movements of five female Artibeus jamaicensis from the day roost in the Pena Blanca light tower to BCI and other nearby areas.
116 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
4 6
4 5
« • • • • » • • • • '
2 3 kilometers
FIGURE 7-20.—Frequency of occurrence of five Artibeus jamaicensis from the day roost in the Pena Blanca light tower in nearby 0.5 km squares.
NUMBER 511 117
5 5
5 4
5 3
5 2
5 1
5 0
4 9
4 8
4 7
4 6
4 5
52 53 54 45 46 47 48 49 50
I . . . •! . . . .