Our effort consisted of 6,053
effective trap-nights between 06 August 2010 and 16 November 2010; we deleted
128 ineffective trap-nights during which a trap was considered mechanically
non-functional or improperly baited. Water levels in portions of the trapping area rose steadily
during early parts of the experiment, and traps in the southern tree islands were
in 3 - 15 cm of water for much of the experiment.
Three Burmese pythons were captured in traps (Table 1), ranging in size from 1740 to 2240 mm SVL and 5840 - 7854 g body mass (Fig. 3). The pythons were captured on 13 Aug, 08 Sep, and 09 Oct; the first two (both males) were
captured in traps equipped with round entrance flaps, and the third (a female) in
a trap with a rectangular entrance. All three were captured in the trap grid of 40 traps.
We captured 69 non-target
organisms in traps, for an overall incidental capture rate of 0.011 per
trap-night. Most of these were
rodents [native cotton rats (Sigmodonhispidus) and non-native roof rats (Rattus rattus)], but we also captured 4 species of frogs and 3 species of snakes (Table 2). Some of these 'captures' were of animals capable of entering and leaving the traps through the mesh at will, including small frogs and small native snakes. We observed no mortality of non-target organisms, all of which were released nearby.
Fig. 3. A Burmese python captured in a trap during the experiment. [larger image]
Visual searching
No pythons were observed during standardised morning visual searches, but two pythons were observed opportunistically while conducting field activities at the study site (Table 1). The first was observed on a canal bank along the west edge of the site, and the second was observed ~5 m from a trap but was not captured in that trap. Standardised visual searching resulted in observations of low numbers of non-target species (rats, hylid and ranid frogs, and native snakes; Table 2).
Post-trapping site treatment
Eleven P. molurus were discovered during vegetation management activities
after the trap trial (0.136 pythons exposed/ha harrowed); ten of these were
discovered by following behind the disc harrow, but one was found on the edge
of the study site along an access road. These pythons averaged 1705 ± 481 mm SVL (range 970 -
2300) and 4712 ± 3074 g (range 718 - 9120; Table 1), and none were recaptures from trapping. Two pythons were killed outright by the harrow, and two more died shortly after capture from harrow-induced injuries. Of those remaining, a few sustained minor injuries (from which we judged they likely would have recovered) and the remainder escaped visible injury (all pythons were humanely euthanized after capture). Among non-target species, 27 live or dead snakes of six species were discovered during harrowing operations (Table 2). In addition, hundreds of rats (Rattus and Sigmodon, not identified to species) were seen fleeing from, or were
killed by, the harrow each day.
Table 1. Characteristics of 16Burmese pythons (Python molurus bivittatus) captured or observed in the Frog Pond area east of Everglades National Park, Florida, during and immediately after the trap trial.
TRAP = captured in python trap, OVE = opportunistic visual encounter, DISC = collected by following disc harrow after trial. No pythons were observed during standardised visual surveys. SVL = snout to vent length
Date
Method
of capture
Sex
SVL
(mm)
Mass
(g)
Notes
13
Aug 2009
TRAP
♂
1740
5840
08
Sep 2009
TRAP
♂
2240
7854
09
Oct 2009
TRAP
♀
1980
6160
29
Oct 2009
OVE
Unk.
~1250
Unk.
Moving
across transect
13
Nov 2009
OVE
Unk.
~2000
Unk.
Motionless
in grass
17
Nov 2009
DISC
♂
1690
4378
Live, died later
18
Nov 2009
DISC
♀
980
718
Live
18
Nov 2009
DISC
♂
1160
1196
Live
18
Nov 2009
DISC
♂
2100
9120
Dead
18
Nov 2009
DISC
♂
1570
2900
19
Nov 2009
DISC
♂
2010
6990
20
Nov 2009
DISC
♀
970
882
Live, died later
20
Nov 2009
DISC
♀
2300
8770
Dead
20
Nov 2009
DISC
♂
1960
7344
Live, along access road
23
Nov 2009
DISC
♂
2210
4984
Live
24
Nov 2009
DISC
♀
1805
4546
Live
Table 2. Species composition and number of individuals of non-target vertebrates captured in python traps (all taxa), observed during visual surveys (exclusive of birds), or exposed by disc harrowing in the Frog Pond area east of Everglades National Park, Florida, between 06 August and 24 November 2010.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:04 PM (KP)