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Effects of a pesticide on tadpole activity and predator avoidance behavior
No abstract available.
Attempted predation of Couch's spadefoot (Scaphicpus couchii) juveniles by ants (Aphaenogaster cockerelli)
No abstract available.
Predation on Corynorhinus townsendii by Rattus rattus
Corynorhinus townsendii (Townsend's big- eared bat) is a rare and declining species. Ex- tensive surveys for the coastal subspecies, C. t. townsendii, in California indicate that only 50% of historic maternity colonies are occu- pied currently (Pierson and Rainey, 1996). Three of the largest maternity colonies occur in Marin Co. Two of these have been moni- tored with evening exit counts on a regular basis since their discovery (1987-Randall House; 1990-Jerrys) through 1996. From 1987 through 1993, the Randall House colony slowly increased from 123 to 215 bats as the colony was afforded greater protection from disturbance once the bats were discovered. Since 1990, both colonies have been com- posed of ca. 200 adult bats in the spring, and ca. 300 adults and young through the summer and early fall.
Management of predator populations with antifertility agents
The search for methods, other than lethal techniques, for controlling predatory animals causing economic losses to the livestock industry prompted investigation of antifertility agents to suppress reproduction. Diethylstilbestrol was selected for initial trials because of its demonstrated antifertility effect on rabbits, mink ( Mustela vison ), dogs, and cattle. In penned tests with stilbestrol, pregnancy was terminated in six coyotes ( C anis latrans ) fed a single 100-mg oral dose dissolved in tallow. A subsequent field trial was conducted in New Mexico on 20 townships, March 5-15, 1963. Five thousand (100 mg stilbestrol in ½ ounce of tallow) drop baits were placed wherever coyote sign was found. After a delay of 3 weeks to allow the drug to take effect, a collection of female tracts from the treated area and a reference area 25 miles away was made to measure and compare reproductive success. Of the 20 females in reproductive condition recovered from the treated area, only 4 had viable embryos, while reproduction was blocked in 16 specimens by failure of implantation or resorption of embryos. All of the 13 females in reproductive condition from the reference area would have produced pups as evidenced by viable embryos. Future tests are scheduled to determine effects on other species and to confirm results on coyotes under a variety of field conditions.
White-tailed deer migration and its role in wolf predation
Seventeen white-tailed deer ( Odocoileus virginianus ) were radio-tagged in winter yards and tracked for up to 17 months each (881 locations) from January 1973 through August 1974 in the central Superior National Forest of NE Minnesota following a drastic decline in deer numbers. Ten vyolves ( Canis lupus ) from 7 packs in the same area were radiotracked before and/or during the same period (703 locations). Deer had winter ranges averaging 26.4 ha. Spring migration took place from 26 March to 23 April and was related to loss of snow cover. Deer generally migrated ENE in straight-line distances of 10.0 to 38.0 km to summer ranges. Two fawns did not migrate. Arrival on summer ranges was between 19 April and 18 May, and summer ranges varied from 48.1 to 410.4 ha. Migration back to the same winter yards took place in early December, coincident with snow accumulation and low temperatures. Social grouping appeared strongest during migration and winter yarding. Survival of the radio-tagged deer was studied through 1 May 1975. Four deer were killed by wolves, one was poached, and one drowned. Mean age of the captured deer was 5.4 years and estimated minimum survival after capture was 2.6 years, giving an estimated total minimum survival of 8.0 years. This unusually high survival rate appeared to be related to the fact that both winter and summer ranges of these deer were situated along wolf-pack territory edges rather than in centers. In addition, most summer ranges of the radio-tagged deer were along major waterways where the deer could escape wolves.
Predation strategies of larval clownfish capturing evasive copepod prey
Fish larvae depend on finding and capturing enough prey for rapid growth during the planktonic phase. The diet of many fish larvae is dominated by copepods, small crustaceans that are highly sensitive to hydrodynamic disturbances and possess strong escape responses. We examined how fish larvae with immature jaws, musculature and fins capture such evasive prey. The kinematics of feeding attempts by larval clownfish Amphiprion ocellaris on 3 developmental stages of copepod Bestiolina similis were investigated using high-speed videography. A stealthy approach brought the fish larva within ~1 mm of the copepod; shortest distances were observed in early larvae (1 to 5 d post-hatch [dph]) attacking immature copepods. Peak speeds during strikes increased with fish age and copepod developmental stage (150 to 250 mm s -1 ), with time to capture <8 ms on average. Most successful captures (70%) were of copepods that failed to initiate an escape response during the strike. If a copepod initiated an escape, capture success decreased to ~50% for nauplii and copepodites and 25% for adults. Adult copepods were more likely to attempt an escape response than copepodites or nauplii. Prey stage and the interaction between strike distance and speed were the parameters that best fit a logistic regression model to the observed captures and escapes. The successful switch to larger and more evasive copepod prey by A. ocellaris larvae did not occur until 7 dph and coincided with ontogenetic changes (post-flexion) and a predatory strategy that included shorter approach phases and greater strike speeds.
To catch a (marsh) predator: Modified trapping methods for breeding and wintering Northern Harriers (Circus hudsonius)
Although there are a variety of methods available for trapping raptors, some species, such as Northern Harriers ( Circus hudsonius ), are not easily captured with standard methods. We tested several existing trapping methods and modified two of them based on Northern Harrier ecology and behavior across seasons in a study population in California. No previously successful methods described in the literature were effective for our study population. Two modified methods were most effective for trapping Northern Harriers: (1) placing two dho-gazas around the nest in a V-shape and flushing the adult female into the nets during the breeding season, and (2) using remote-triggered bow nets baited with waterbird carcasses in winter. Dho-gazas at the nest worked well during the early nestling-rearing stage, when nestlings were younger than 2 wk old and adult females were most attentive. This method was not suitable during the incubation stage because Northern Harriers are prone to nest abandonment. In the winter, Northern Harriers are known to scavenge, yet this aspect of their behavioral ecology has previously been rarely exploited for trapping purposes. These two methods allow for selective Northern Harrier trapping across seasons and provide modified options for research on this understudied and declining species in North America.
Editorial: Ecological and behavioral traits of apex predators in oceanic insular ecosystems: Advances and challenges in research and conservation
No abstract available.
Exotic predators may threaten another island ecosystem: A comprehensive assessment of python and boa reports from the Florida Keys
Summarizing historical records of potentially invasive species increases understanding of propagule pressure, spatiotemporal trends, and establishment risk of these species. We compiled records of non-native pythons and boas from the Florida Keys, cross-referenced them to eliminate duplicates, and categorized each record’s credibility. We report on 159 observations of six python and boa species in the Florida Keys over the past 17 years. Burmese pythons (Python bivittatus), boa constrictors (Boa constrictor), and ball pythons (Python regius) are the most frequently reported species, but credible records of three additional species were also reported. Among the most notable records, we report on three hatchling and multiple reproductive Burmese pythons captured on North Key Largo since 2016, indicating that the species is now established on that island. The expanding mainland Burmese python population and ongoing python and boa introductions via pet and cargo pathways are likely to keep propagule pressure high in coming years. Both effective public outreach to solicit reporting of sightings and effective early detection and rapid response networks may help to prevent further establishment and associated ecological impacts of python and boa species in the Florida Keys.
Surface material and snout-vent length predict vertical scaling ability in brown treesnakes:an evaluation of multispecies barriers for invasive species control on Guam
The combination of snake-proof barriers and an aerial toxicant delivery system for snake suppression may allow large-scale control of invasive brown treesnakes (Boiga irregularis) on Guam. However, suppression or local eradication of several other species (e.g., introduced ungulates, cats, rodents) may be required for successful restoration and recovery of forest habitat and reintroduction of native fauna. Island-wide eradication of invasive species is unlikely on Guam, and existing snake-proof barriers are largely ineffective against cats, rodents, shrews, or monitors. Improved barrier technology and pest-control tools may together provide a viable solution to support localized restoration of species and habitats. We designed and tested prototype multispecies barriers using materials known to repel ungulates, cats, and rodents, with a focus on testing the ability of a rolled hood installed over three different mesh designs to repel brown treesnakes and black rats (Rattus rattus). Woven wire (4.9 × 12 mm aperture, 2.5 mm dia. wire) repelled 99.1% of all snakes, including ≥1031 breach attempts by 112 individuals and 2 successful breaches by 1 small individual. Woven wire (6 × 6 mm aperture, 2.7 mm dia. wire) repelled 100% of all snakes, including 611 breach attempts by 65 individuals. Mini chain link mesh (7 × 9 mm aperture, 1 mm dia. wire) repelled 100% of all snakes, including 1053 breach attempts by 97 individuals. Brown treesnakes were unable to climb either of the two woven wire designs (1642 breach attempts by 160 individuals), making the rolled hood serve as a redundant secondary snake barrier. The rolled hood repelled 100% of all snakes when individuals were provided a climbable surface to access the hood (94 breach attempts by 39 snakes). The probability of a snake being able to climb the mini chain link mesh was inversely related to SVL. The rolled hood repelled 100% of all rats, with 5079 breach attempts by 21 individuals. Recommended next steps include consultation with engineers to address wind loading, structural integrity, material interactions, and integration of decision support tools to optimize cost and efficacy of barrier designs on the landscape.
Predation by Acanthurus leucopareius on black-band disease in Kauai, Hawaii
No abstract available.
Pathology of mouse (Mus musculus) predation on Laysan albatross (Phoebastria immutabilis) on Midway Atoll National Wildlife Refuge
Invasive rodents on islands have adverse effects on native birds in island ecosystems, and rats are the most common culprits. Recently, house mice ( Mus musculus ) in the South Atlantic were found preying on three species of albatross chicks. Here, we show that house mice can also prey on nesting adult Laysan Albatross ( Phoebastria immutabilis ) on Midway Atoll National Wildlife Refuge (US). In contrast to mouse attacks on albatross in the South Atlantic, where mice targeted the rump and crown of chicks, on Midway, mice targeted nesting adults mainly on the back. For both regions, the outcome was similar with reduced nesting success. In the case of Midway, reduced nesting success was due to nest abandonment or mortality of one or both parents because of secondary bacterial infections. Mouse-induced mortality of adult albatross has the potential to have a more potent demographic effect because of their much higher natural survivorship once they reach adulthood.
Effects of predator exclosure design on duck brood movements
No abstract available.
Protecting duck nests from mammalian predators with fences, traps, and a toxicant
Abstract has not been submitted
Assessing factors that may predispose Minnesota farms to wolf predation on cattle
Wolf (Canis lupus) depredations on livestock cause considerable conflict and expense in Minnesota. Furthermore, claims are made that such depredations are fostered by the type of animal husbandry practiced. Thus, we tried to detect factors that might predispose farms in Minnesota to wolf depredations. We compared results of interviews with 41 cattle farmers experiencing chronic cattle losses to wolves (chronic farms) with results from 41 nearby matched farms with no wolf losses to determine farm characteristics or husbandry practices that differed and that therefore might have affected wolf depredations. We also used a Geographic Information System (GIS) to detect any habitat differences between the 2 types of farms. We found no differences between chronic and matched farms in the 11 farm characteristics and management practices that we surveyed, except that farms with chronic losses were larger, had more cattle, and had herds farther from human dwellings. Habitat types were the same around farms with and without losses. The role of proper carcass disposal as a possible factor predisposing farms to wolf depredations remains unclear
Snowy owl predation on lapland longspur nestlings recorded on film
During the summer of 1971 I investigated the breeding biology of the Lapland Longspur, Calcarius lapponicus , near Barrow, Alaska. To obtain data on incubation and feeding patterns of nesting longspurs, time-lapse cameras (Minolta Autopak-8 D6 super-8 movie cameras equipped with an Intervalometer-P time-lapse device) were positioned at several nests throughout the nesting season with an exposure interval of either 8 or 30 seconds. At 07:00 on 14 July a Snowy Owl, Nyctea scandiaca , took the three largest of four young at a nest being monitored at 30-second intervals (Figure 1). The nestlings were 4, 6, 7, and 8 days posthatching and weighed approximately 12, 15, 20, and 20 g respectively on 13 July.