Suchergebnisse

3 pages.-- PMID: 7760485 [PubMed]. ; We determined the prevalence of Dirofilaria immitis (Nematoda, Filariidae) among 433 red foxes (Vulpes vulpes) in northeastern Spain, between 1990 and 1992. Forty-six (11%) of 433 foxes were infected; the intensity ranged from 1 to 36 (mean ± SE; 4.39 ± 0.92) nematodes per host. The prevalence of D. immitis was higher in foxes inhabiting riparian zones of the study area. This population has a very high juvenile/adult ratio. Heartworm prevalences did not differ among host sex, weight, or fat condition categories. ; The fieldwork was partially financed by the Government of Aragón, Programme 533.1 of Fauna Conservation. ; Peer reviewed

Context
The European red fox (Vulpes vulpes) is subject to control by poison baiting in many parts of its range in Australia to protect both native and domestic species. Assessments of baiting programs can improve their effectiveness and help ensure that long-term control outcomes are achieved.

Aims
We describe spatial and temporal patterns of bait uptake by the red fox in remnant forest within an agricultural matrix, including multiple bait-takes and hotspots of activity over time, and examine the response of foxes to baiting operations.

Methods
We analysed bait uptake (Foxoff®) from 12 baiting operations over 5 years in the Goonoo forest, a 62 500 ha remnant surrounded by cleared land in central New South Wales, Australia. More than 8000 checks of bait-stations were analysed to provide indices of fox activity per bait-check, patterns of bait removal during bait-checks, and bait uptake at stations within and across operations. Fox activity was also assessed before and after four operations using sand plots.

Key results
There was no consistent decline in relative fox activity in relation to changes in bait-take; increases in the activity index occurred in successive checks within most operations. Spatial analyses of checks within control operations showed that consecutive baits were removed at more than 70% of bait stations that were visited by foxes. Temporal analyses showed further that within an operation, multiple bait-takes occurred at ~20% of stations and, across all operations, hot spots of activity could be identified.

Conclusions
A short (2-week) baiting window in standard baiting operations may not be effective in reducing the activity of foxes across the landscape. It is likely that many baits are being cached during each operation, and that foxes move into the baited area from unbaited surrounding areas.

Implications
More frequent and timely baiting operations are needed to achieve maximum disruption to the fox population in the remnant forest environment, at least as indicated by patterns of bait-take. Increasing the distance between baits, to ~1.5 km, while reducing baiting-gaps at the landscape scale, will also be important to reduce caching and still ensure that baits are encountered.

The European red fox is an introduced pest species in Australia for which improved means of control are urgently needed. Research efforts have focussed recently on the development of novel biological control methods to reduce the serious impact this species continues to have on both native fauna and the sheep industry. The ultimate goal has been to generate an antifertility vaccine for use on foxes that relies on a process termed 'immunocontraception'. A variety of proteins derived from sperm and oocytes, together with different delivery vectors, have been experimentally assessed for their ability to induce immunocontraceptive responses in foxes. Vaccine vectors screened have included Salmonella typhimurium, vaccinia virus and canine herpesvirus but suppression of fertility has yet to be achieved with any combination of antigen and delivery vector. Downregulation of fox mucosal antibodies during oestrus, lack of vector replication and low antibody responses to the target antigens have been the main constraints in successful fertility control. The fox is not well known as an experimental animal and the logistics of dealing with this difficult-to-handle species proved to be a major challenge when compared with other species, such as rabbits and mice. Despite these difficulties, research on fox immunocontraception has generated important insights into the reproductive biology, husbandry, biology and basic immunology of viral vectors in European red foxes. This information represents a valuable knowledge base should antifertility vaccination for foxes be revisited in the future.

The factors that affect the trappability of the red fox
(Vulpes vulpes L.) in alpine and subalpine New South
Wales were examined by means of treadle snares. Trapping (1) on animal tracks
without the use of a bait or lure, and (2) by setting snares around a bait,
led to the capture of individuals of both sexes and all age-classes. A greater
number of foxes was captured per number of snares set in winter than in other
seasons because of the commensal foraging patterns of foxes at this time.
Foxes were more likely to be caught within 100 m of their home-range
boundaries during snow-free months and outside their home ranges while
foraging at ski resorts in winter. Snares were found to be difficult to set,
and foxes were captured in only 50% of sprung snares. Treadle snares
caused no apparent long-term injuries to 40 red foxes that were radio- tracked
and observed for 1–24 months after capture.

Abstract Context The use of baits for reducing the populations of harmful animal species, eradicating invasive species, vaccination, contraception or producing conditioned aversion, is widespread worldwide. However, baiting programs are often not successful enough and affect non-target species, requiring new approaches for baiting methods. Aims The aim of the present study was to evaluate two attractants used in carnivore studies to improve bait intake probability by red foxes and minimise bait intake by non-target species. Methods Non-toxic baits were distributed across 1000 ha, with bait intake monitored by camera traps during 3-week trials. Baits were assigned to two treatments with lures (lynx urine and Fatty Acid Scent – FAS) and one control. Bait intake by red foxes and non-target species was analysed using Generalised Linear Mixed Model (GLMM) and Kaplan–Meier survival analyses. Key results Lynx urine significantly increased the bait intake by red foxes (58.8%) compared with control (5.7%) and FAS (16.7%) treatment. However, FAS did not significantly increase the bait intake by red foxes compared with control. Bait intake by non-target species differed significantly between treatments, with lower intake in lynx urine (23.5%) treatment than control (54.7%), but not regarding FAS (36.7%), and neither between FAS and control. The probability of bait persistence after the 3-week trial period differed significantly among treatments, being lower in lynx urine treatment (0.18) than FAS (0.50) and control (0.43). All baits taken by foxes with lynx urine treatment (58.8%) occurred within the first 10 days, whereas intake by non-target species (23.5%) stopped after Day 7. Conclusions The use of lynx urine lure increased the proportion of baits consumed by red fox and reduced bait intake by non-target species. Implications Lures can serve to optimise bait delivery methods for red foxes in their different applications, such as conditioned aversion studies, vaccination, live trapping or predator control, while minimising risks to non-target species and reducing the costs and application time.

Three adult red foxes (Vulpes vulpes) in a 20-km2 wilderness area of coastal south-eastern Australia
were studied during pre-denning and denning. Home ranges were defined by geographic featues, but
not by roads. The foxes occupied exclusive home ranges, and observations suggest that they were
territorial and existed alone or, at most, in mated pairs. Home-range sizes were small (1.2-5.2 km2)
compared with those in North America and Europe, but similar to those in England and Wales.
During denning the female's activity became almost entirely diurnal. When not active, the vixen
was with the cubs. Male activity during denning was nocturnal, but, as found for the female, inactive
periods were spent near the suspected den-site in his home range.
Habitats that were frequented most by all foxes were those with the highest abundance of either
small or medium-sized mammals. Dry sclerophyll forest was used consistently by all foxes but heathland
and the beaches were rarely frequented. Small and medium-sized mammals, which were abundant in
all habitats except the beach and heathland, made up 52.6% of items in the scats.

Context The Eurasian red fox (Vulpes vulpes) is a widespread pest in mixed agricultural and remnant forest habitats in southern Australia, and is controlled most commonly with baits containing poison (1080) to protect both agricultural and ecological assets. An understanding of fox movements in such habitats should assist in the strategic placement of baits and increase bait encounters by foxes across the landscape, thus improving the success of control efforts. Aims We seek to understand the ranges, movements and habitat use of foxes to aid the development of effective management plans. The fate of tracked animals was examined during a control program. Methods We radio-tracked 10 foxes using VHF transmitters and three foxes using GPS receivers during control operations in a remnant forest area near Dubbo, New South Wales. We used VHF location fixes to estimate fox range areas and GPS fixes to describe temporal and spatial aspects of fox movements and range use, focal points of activity and potential bait encounters. Selection of forest versus cleared areas was assessed, as was the impact of control operations on collared foxes. Key results Range areas (mean ± s.e.; 95% minimum convex polygon) for VHF- and GPS-tracked foxes were 420 ha ± 74 and 4462 ha ± 1799 respectively. Only small parts of range areas were visited on a daily basis, with little overlap. Animals were often within 200 m of roads and crossed or travelled on roads more than expected. At least 75% of collared foxes were probably poisoned in the control program. Conclusions Foxes occupy large ranges and move long distances in the study region, with little daily overlap, so successful defence of range areas is unlikely. Control efforts successfully poisoned foxes but also limited data collection because of reduced tracking periods. Implications The large and variable areas occupied by foxes suggested that control efforts need to be on-going, coordinated across the landscape, and use a minimum bait density of 0.5 baits per 100 ha in remnant forest habitat to ensure that gaps are minimised. Control operations should target roads and forest edges for bait placement, and increase the time that baits are available, to increase fox encounters and maximise the success of control efforts.

AbstractWith urban encroachment on wild landscapes accelerating globally, there is an urgent need to understand how wildlife is adapting to anthropogenic change. We compared the behaviour of the invasive red fox (Vulpes vulpes) at eight urban and eight peri-urban areas of Sydney, Australia. We observed fox behaviour around a lure and compared fox activity patterns to those of potential prey and to two domestic predators (dogs—Canis lupus familiaris and cats—Felis catus). We assessed the influence of site type, vegetation cover, and distance from habitation on fox behaviour, and compared the temporal activity patterns of urban and peri-urban red foxes. Urban red foxes were marginally more nocturnal than those in peri-urban areas (88% activity overlap). There was greater overlap of red fox activity patterns with introduced mammalian prey in urban areas compared with peri-urban areas (90% urban vs 84% peri-urban). Red fox temporal activity overlapped 78% with cats, but only 20% with dogs, across both site types. The high degree of overlap with cats and introduced mammalian prey is most likely explained by the nocturnal behaviour of these species, while pet dogs are generally kept in yards or indoors at night. The behavioural differences we documented by urban red foxes suggest they may adapt to human modifications and presence, by being more nocturnal and/or more confident in urban areas.

Context Predation is one of the key contributors to mortality in freshwater turtles. Confirming the identity of predators is an important step towards conservation management action. Throughout Australia, the red fox (Vulpes vulpes) is suspected to apply significant and unsustainable predation pressure to turtle populations, killing adults and depredating nests; however methods for confirming this are limited. Aims The present study used a range of methods to confirm predation of oblong turtle (Chelodina colliei) nests and adults by the introduced red fox. Methods First, depredated adult carapaces, and turtle egg-shell fragments from excavated nests were swabbed and analysed for trace DNA. Second, we used artificial turtle nests, monitored by camera traps, to analyse seasonal changes in the behaviour of foxes around sites where turtle nests are present, including over the nesting season. Last, we used scat analysis to identify the prevalence of turtle remains in fox diet. Key results Predominantly fox DNA was recovered from both adult carapaces and depredated eggs. In addition, camera traps recorded only foxes depredating artificial nests. Despite this evidence that foxes kill adults and excavated nests, we found that turtle remains were only a small part of the diet of foxes at this study site (hatchling or turtle egg shell were present in only 4% of 230 scats sampled). The diet of these foxes was largely anthropogenic-sourced foods, such as fruit (e.g. figs, grapes, melons; 81% of scats), sheep carrion (41%) and rodents (36%). Conclusions We conclude that DNA analysis, camera trapping and scat analysis are effective methods of identifying foxes as predators of adult turtle, and their nests. Furthermore, we found that anthropogenic foods (orchard crops, livestock or synanthropic species) may subsidise greater fox population size than might occur in their absence, thereby increasing potential pressure on these freshwater turtles. Implications Our findings give credence to the argument that foxes are effective predators of turtle adults and nests. In addition, the high proportion of anthropogenic food sources in the diet of foxes, and potential subsidisation, is an important consideration for land managers.

The absolute and relative contribution to the finite rate of increase of
specific age classes was examined using projection matrix sensitivity and
elasticity analysis for a number of red fox
(Vulpes vulpes) populations. The fox populations that
were examined included urban foxes from England, rural foxes from North
America and rural foxes from Australia. The youngest age classes made the
greatest contribution to the finite rate of increase for all populations
studied. A pest management strategy that reduces survivorship and fertility of
juvenile and young adult foxes (Age Classes 1 and 2) will be the most
effective strategy for reducing a population's finite rate of increase.
The results indicate that fertility control may be as effective as lethal
methods for controlling some fox populations.

The suitability of spotlight counts to index red fox abundance was assessed in
an arid environment through a comparison with a scat deposition index (active
attractant). In most cases there was a high degree of correlation between the
two indices, suggesting that the spotlight counts were accurately documenting
fluctuations in population size. However, the precision of the spotlight index
was often low (c.v. = 0.07–0.46), suggesting that the technique
may not allow the statistical detection of small changes in abundance. During
periods when there was an influx of new individuals into the population, the
seasonal scat index displayed a three-month time lag in documenting abundance
while foxes accustomed themselves to the presence of the regular food supply.
The level of precision of the scat index was also found to be relatively low
(c.v. = 0.21–0.48). Nevertheless, further refinements of this
technique may produce a suitable measure of fox abundance.

In a free-choice experiment conducted in a series of pen trials, the influence
of food preference on caching behaviour by the red fox
(Vulpes vulpes) was investigated for three unpoisoned
bait types: deep-fried beef liver (DFL), dried deep-fried beef liver (DDFL)
and a commercial bait (Foxoff®). Although some variation in individual
preferences for the DDFL and Foxoff was observed, all of the foxes in the pen
trials preferred the DFL (P < 0.01) and all cached it
least often (P < 0.01). Field trials then compared
the uptake, consumption and incidence of caching for the most preferred (DFL)
and least preferred (Foxoff) bait types. Radio-transmitters were inserted into
unpoisoned Foxoff and DFL baits and a free choice of either was provided at
bait stations at three independent sites. A clock module recorded the precise
time that each bait was taken from the bait station. The fate of each bait (it
could either be eaten, cached or remain in situ) was
recorded daily and baits were replaced for five consecutive nights. There was
no difference in the rate of uptake for the two baits (P
> 0.05) and, despite some variation between the sites, DFL was the most
often eaten (P < 0.001) and Foxoff the most often
cached (P < 0.001). These data strongly suggest that
a highly palatable bait will increase the likelihood of rapid consumption of
baits and reduce the incidence of caching. This is likely to increase the
cost-effectiveness of baiting and limit the potential for nontarget impacts
due to the movement of baits. The high degree of concordance between the
results of the pen and field trials suggests that pen trials can assist in the
development of more effective bait types. However, conclusions about the
relative efficacy of bait types drawn from the results of baiting programs
that measure only bait uptake are unlikely to be reliable.