Evaluation of feral pig control in Hawaiian protected areas using Bayesian catch-effort models

In 2007 The Nature Conservancy (TNC) undertook an intensive ungulate control programme throughout three of its preserves on the Hawaiian islands of Maui and Moloka'i, with one aim being to reduce feral pig numbers to zero or near zero. The preserves were divided into manageable zones and over a 2 to 5 month period hunted from the ground with dogs in a series of up to four sweeps across the zones. More focussed hunting followed at sites with evidence of survivors. We used the data collected by the hunters to evaluate the efficacy of the control programme. The data comprised the number of pigs shot per zone per sweep and the hunters?effort and were used to fit a Weibull catch-effort model within a Bayesian framework. The fitted model provided posterior parameter estimates of the initial number of pigs resident in each zone and the relationship between hunting effort and the probability of detecting (and dispatching) a pig. The large shape parameter estimate indicated that the probability of detecting a pig increased substantially with cumulative hunting effort or experience in that zone. The control programme was successful in six out of eight of the control zones reducing pig numbers to zero or one per zone (equating to <1 pig per km²) but was less successful in two zones where an estimated 9?14 pigs remained. However there were large credible intervals around some of the parameter estimates, suggesting an additional source of variation that was not captured by the current model. We suggest this was due to immigration of pigs back into the preserves. The quantified relationship between search effort and the probability of detecting a pig was used to make predictions on how much effort is required to detect all pigs, and can be used by TNC to interpret future monitoring data.     

Big game hunting in New Zealand: per capita effort,harvest and expenditure in 2011–2012

Recreational big game hunters make a significant contribution to conservation through kills of deer, pigs, chamois and tahr. New opportunities for managing recreational hunting through the proposed Game Animal Council underscore the need to understand the implications of potential changes in recreational hunting participation and harvests. Based on a survey of hunters' recall over a year, hunters averaged 15.63 (SEM = 0.58) big game hunts per year, spending 30.53 (SEM = 0.85) days hunting and killing 8.92 (SEM = 0.69) big game animals. Hunters commonly targeted several species on a single hunt, with highly skewed distributions for hunter effort and kills. Mean monthly expenditure on big game hunting items was $296.78 (SEM = $8.95). Results demonstrate that big game hunting is a significant activity in New Zealand, but this varies considerably among hunters with a small number responsible for the vast majority of kills. These are important considerations for future big game hunting management.     

Demographic influences on the hunting behavior of chimpanzees

We investigated hunting in an unusually large community of wild chimpanzees at Ngogo in the Kibale National Park, Uganda. Aspects of predation were recorded with respect to the prey, the predators, and hunting episodes. During 23 months of observation, the Ngogo chimpanzees caught 128 prey items from four primate and three ungulate species. Chimpanzees preyed selectively on immature red colobus primarily during group hunts, with adult males making the majority of kills. Party size and composition were significant predictors of the probability that chimpanzees would hunt and of their success during attempts. Chimpanzees were more likely to hunt red colobus if party size and the number of male hunters were large; party size and the number of male hunters were also significantly larger in successful compared with unsuccessful hunts. The Ngogo chimpanzees did not appear to hunt cooperatively, but reciprocal meat-sharing typically took place after kills. Hunts occurred throughout the year, though there was some seasonality as displayed by periodic hunting binges. The extremely high success rate and large number of kills made per successful hunt are the two most striking aspects of predation by the Ngogo chimpanzees. We compare currently available observations of chimpanzee hunting behavior across study sites and conclude that the large size of the Ngogo community contributes to their extraordinary hunting success. Demographic differences between groups are likely to contribute to other patterns of interpopulation variation in chimpanzee predation. Am J Phys Anthropol 109:439–454, 1999. © 1999 Wiley-Liss, Inc.     

The decline of the otter Lutra lutra L. in Britain: an analysis of hunting records and discussion of causes

The records of one pack of Otter Hounds hunting in southwest England are examined for the period 1907 to 1971 as well as the records of all packs active in Britain between 1950 and 1976. The hunting success per unit effort varies from year to year depending on changes in hunting conditions but longer term changes can also be identified. The hunting success of the Culmstock Otter Hounds (hunting in parts of south-west England) increased steadily from 1907 to 1956 but in most of England and south Wales the success rate of the hunts declined rapidly after 1957. There was also a decline in success in northern England and southern Scotland but to a lesser extent, while in north Wales and Eire, there is no evidence for a decline.
These changes are considered to reflect changes in otter populations but the extent of the decline in hunting success (to between 37% and 55% of previous levels in the southern hunts) is probably less than the actual decline in otter numbers. There are no signs of a recovery in the population but indications of a continuing decline up to 1976.
The reason for the increasing population in the first half of the century in south-west England is probably the decrease in persecution since the nineteenth century. A variety of causes for the crash in the late 1950s are considered and the factor most likely to be responsible is the introduction of the dieldrin group of insecticides in 1956. Use of these compounds has been increasingly restricted since 1963 and the possible reasons for the failufe of the otter population to recover are listed but no firm conclusions can be drawn as yet.     

Hunting mode and success of African Peregrines Falco peregrinus minor,does nesting habitat quality affect foraging efficiency?

Peregrine Falcon Falco peregrmus hunting behaviour was studied at nest-sites in three areas of South Africa over eight years. In Africa, resident Peregrines are mostly restricted to high cliffs, possibly because these structures provide optimal conditions for hunting. This hypothesis is examined in terms of the influence of nest-site quality, particularly cliff height, on foraging efficiency. Foraging mode varied considerably between sites, and males foraged more actively than females but there was little variation in the design of hunts between sexes, seasons or study areas. Individually, Peregrines spent 30–50% of the day on or near the nest cliff. On average, about 0.5 hunts were recorded per hour of observation. Foraging mode was not correlated with cliff height or elevation above the surrounding terrain, but Peregrine pairs occupying higher cliffs achieved greater hunting success rates. Most hunts were initiated from elevated perches on the nest cliff, and perch hunts were more successful than strikes made from the air. Success was highest in strikes at doves and small passerines, and over habitats with moderate cover. The height difference between Peregrine and prey at the start of a hunt positively and significantly affected hunting success. Overall, Peregrines were relatively sedentary and made extensive use of the nesting habitat as a foraging area. High nest cliffs contributed to foraging success by providing perch-hunting falcons with an effective height advantage over their prey.     

Hunting Behavior of Chimpanzees at Ngogo,Kibale National Park,Uganda

Chimpanzees (Pan troglodytes) prey on a variety of vertebrates, mostly on red colobus (Procolobus spp.) where the two species are sympatric. Variation across population occurs in hunting frequency and success, in whether hunting is cooperative, i.e., payoffs to individual hunters increase with group size, and in the extent to which hunters coordinate their actions in space and time, and in the impact of hunting on red colobus populations. Also, hunting frequency varies over time within populations, for reasons that are unclear. We present new data on hunting by chimpanzees at Ngogo, Kibale National Park, Uganda, and combine them with earlier data (Mitani and Watts, 1999, Am. J. Phys. Anthropol. 109: 439–454) to examine hunting frequency and success, seasonality, and cooperation. The Ngogo community is the largest and has the most males of any known community. Chimpanzees there mostly hunt red colobus and are much more successful and make many more kills per hunt than at other sites; they kill 6–12% of the red colobus population annually. The number of kills and the offtake of meat per hunt increase with the number of hunters, but per capita meat intake is independent of hunting party size; this suggests that cheating occurs in large parties. Some behavioral cooperation occurs. Hunting success and estimated meat intake vary greatly among males, partly due to dominance rank effects. The high overall success rate leads to relatively high average per capita meat intake despite the large number of consumers. The frequency of hunts and of hunting patrols varies positively with the availability of ripe fruit; this is the first quantitative demonstration of a relationship between hunting frequency and the availability of other food, and implies that the chimpanzees hunt most when they can easily meet energy needs from other sources. We provide the first quantitative support for the argument that variation in canopy structure influences decisions to hunt red colobus because hunts are easier where the canopy is broken.     

‘Impact hunters’ catalyse cooperative hunting in two wild chimpanzee communities

Even when hunting in groups is mutually beneficial, it is unclear how communal hunts are initiated. If it is costly to be the only hunter, individuals should be reluctant to hunt unless others already are. We used 70 years of data from three communities to examine how male chimpanzees ‘solve’ this apparent collective action problem. The ‘impact hunter’ hypothesis proposes that group hunts are sometimes catalysed by certain individuals that hunt more readily than others. In two communities (Kasekela and Kanyawara), we identified a total of five males that exhibited high hunt participation rates for their age, and whose presence at an encounter with red colobus monkeys increased group hunting probability. Critically, these impact hunters were observed to hunt first more often than expected by chance. We argue that by hunting first, these males dilute prey defences and create opportunities for previously reluctant participants. This by-product mutualism can explain variation in group hunting rates within and between social groups. Hunting rates declined after the death of impact hunter FG in Kasekela and after impact hunter MS stopped hunting frequently in Kanyawara. There were no impact hunters in the third, smaller community (Mitumba), where, unlike the others, hunting probability increased with the number of females present at an encounter with prey.     

Net hunters vs. archers: Variation in women's subsistence strategies in the Ituri Forest

BaMbuti of the Ituri Forest, Zaire, employ two primary hunting techniques: net hunting, in which women routinely participate, and bow hunting, in which women rarely participate. We hypothesize that the value of women's labor devoted to different subsistence activities, combined with the exchange value of meat, will determine whether women participate in hunts. Field observations were conducted in four different areas: two exploited by archers and two by net hunters. Results indicate that women in nethunting areas earn more calories per unit time by hunting than by working in agriculturalists' gardens; whereas women in archer areas earn more calories by working for agriculturalists than by hunting. We found no significant difference in the composition or diversity of the forests exploited by net hunters and archers. The results are discussed in light of the longstanding debate concerning the factors that account for distribution of net hunting and archery in the Ituri Forest.     

Harvesting a red-listed species: determinant factors for willow ptarmigan harvest rates,bag sizes,and hunting efforts in Norway

A main objective of game management on public lands in Norway is to ensure that harvest levels are sustainable while securing hunting access to the public. The willow ptarmigan is a popular but red-listed small game species, and it is challenging for managers to optimize harvest levels based on uncertain population estimates and limited knowledge of the factors influencing hunting impact. We studied how willow ptarmigan hunting effort, catch per unit effort, and harvest rates were influenced by ptarmigan density, topography, vegetation, and infrastructure. Data were collected during 2013–2016 from 162 hunting blocks covering 26,828 km² state-owned land in the counties Nordland and Troms, northern Norway. Hunting effort averaged 1.27 days/km² (SD?=?2.08), and it was the highest in areas close to roads and cabins. We found an opposite effect on the catch per unit effort (CPUE, mean?=?0.77 ptarmigan/day, SD?=?0.48), which was lower close to roads. There was a marked positive effect of density on CPUE, whereas terrain steepness (slope) had a negative effect. On average, harvest removed <?10% of the autumn population in the hunting areas during the study period. This indicates a relatively low and partially compensatory hunting mortality in most years and areas. Although this study shows a low harvest rate, we recommend managers to survey ptarmigan populations, hunting effort, and harvest, especially in easily accessible areas close to infrastructure and in periods of low population density.     

Willow grouse bag size is more sensitive to variation in hunter effort than to variation in willow grouse density

Annual variation in harvested animals (hereafter bag size) is often used as an index of population abundance when investigating population dynamics. Few studies have evaluated how well bag size tracks population change despite its widespread use. Two recent studies on grouse harvest statistics have reached contrasting conclusions. Th ere is limited information about the functional response of hunters in relation to varying game densities, and effort is seldom recorded. We investigated how much of the variation in bag size (total number of harvested grouse km^?2) is explained by variation in willow grouse Lagopus lagopus density (adult and young grouse km^?2) and hunting eff ort (total number of hunting days km^?2). We also evaluated catch per unit effort (CPUE) as an index of grouse abundance, and estimated the response in harvest rate (total bag size in relation to total grouse density) to varying hunting effort. We used data from the 88 management areas on state land in Jämtland county, Sweden (1996–2007), where hunting days and bag size are recorded in detail. Willow grouse density was estimated in four of these management areas in August using line transects and distance sampling. The hunting effort and total grouse density explained most of the variation in bag size (R²= 0.89). Bag size was twice as sensitive to changes in hunting effort compared to changes in grouse density. More than a ten times change in the grouse population density was required to one unit change in bag size. The use of CPUE did not provide a better alternative index of grouse density, and variation in density only explained 23% of the variation in CPUE. Harvest rate showed a strong relationship with hunting effort, and we suggest that an upper limit in hunting effort can be used to reduce the risk of high harvest rates. Hunters became more efficient at low densities and controlling hunting effort is most important when there are indications of population lows and/or poor breeding. CPUE may be less sensitive to changes in game abundance than previously assumed, and bag size as a proxy for population density would then depend on the ability of hunters to adjust their effort according to population change. We speculate that this ability will depend on whether or not hunters have long‐term experience of a hunting area where they can return to hunt throughout the hunting season. We propose that recording hunting eff ort should be encouraged and possible correlations with game abundance and other factors such as weather should be investigated for game species.     

Do intensive drive hunts affect wild boar (Sus scrofa) spatial behaviour in Italy? Some evidences and management implications

Wild boar have been increasing in numbers all over Western Europe in the last 30 years. The species is a major pest for agriculture, but it has a high value as a game species, and in Italy, as in several other countries, it is traditionally hunted in drive hunts by hunting teams with several dogs. This hunting method can have disruptive effects on the demography and spatial behaviour of wild boar, especially family groups. We conducted a 2-year study (2003 and 2004) to determine the effects of drive hunt disturbance on the spatial behaviour of wild boar family groups in the Northern Apennines (central Italy). Twenty wild boar belonging to ten family groups were ear tagged with a radio device. We located resting sites daily and used intensive tracking sessions during drive hunts. Three seasons were determined: pre-hunting, hunting and post-hunting. A general pattern of increased spatial instability during the hunting season was shown. Resting ranges were larger, and resting sites were more interspersed. Distances between consecutive resting sites were greater during the hunting season and, especially, on hunting days. The displacement of family groups caused by drive hunts was generally short lived except for those groups that were repeatedly hunted and so abandoned their pre-hunt (native) range. During drive hunts, wild boar showed a moderate tolerance to hunting disturbance, and only family groups which were directly chased by dogs escaped or altered their behaviour. The response of wild boar to hunting disturbance seemed to be highly related to the degree of hunting pressure combined with individual variability. The impact on wild boar behaviour should be reduced, above all by avoiding repeated hunts in the same areas within a short period and by employing well-trained hounds.     

Modelling tropical fire ant (<Emphasis Type="Italic">Solenopsis geminata</Emphasis>) dynamics and detection to inform an eradication project

Invasive species threaten endangered species worldwide and substantial effort is focused on their control. Eradication projects require critical resource allocation decisions, as they affect both the likelihood of success and the overall cost. However, these complex decisions must often be made within data-poor environments. Here we develop a mathematical framework to assist in resource allocation for invasive species control projects and we apply it to the proposed eradication of the tropical fire ant (Solenopsis geminata) from the islands of Ashmore Reef in the Timor Sea. Our framework contains two models: a population model and a detection model. Our stochastic population model is used to predict ant abundance through time and allows us to estimate the probability of eradication. Using abundance predictions from the population model, we use the detection model to predict the probability of ant detection through time. These models inform key decisions throughout the project, which include deciding how many baiting events should take place, deciding whether to invest in detector dogs and setting surveillance effort to confirm eradication following control. We find that using a combination of insect growth regulator and toxins are required to achieve a high probability of eradication over 2 years, and we find that using two detector dogs may be more cost-effective than the use of lure deployment, provided that they are used across the life of the project. Our analysis lays a foundation for making decisions about control and detection throughout the project and provides specific advice about resource allocation.     

Optimal foraging in an amphibious mammal. I. The aqualung effect

The marginal value theorem of Charnov is extended to a simple model covering the case of mammalian carnivores hunting underwater, in which situation their total search time and pursuit effort is constrained by the limited oxygen capacity of their lungs. In the mink Mustela vison hunting rudd in an experimental tank the duration of dives, of giving-up times, and of the pursuit phase of underwater hunts, as well as the frequency of dives, were consistent with the usual marginal value predictions. Giving-up times were also essentially constant within bouts, as expected. An interaction between foraging economics and oxygen reserves derived from the extended model was confirmed experimentally.     

Effect of growth temperature and total non-structural carbohydrate accumulation on growth coefficient in Petunia x hybrida petals

It is widely believed that growth coefficient [g, respiratory cost consumed for synthesis of a unit dry weight (DW)] is independent of growth temperature. However, some studies using regression analysis indicated an increase in g at high temperatures. These two conflicting conclusions may be affected by the differences in total non-structural carbohydrate (TNC) accumulation between growth temperatures. Here, we evaluated whether g is independent of growth temperature in Petunia x hybrida petal after excluding TNC from DW. We also examined changes in g during petal development. We measured amounts of carbon, nitrogen, minerals and TNC and theoretically estimated construction cost and g. The results showed that the estimated g greatly changed with age and differed between growth temperatures. The estimated g was markedly increased by excluding TNC from DW. The effect of accumulation of TNC on the estimated g was observed at later stage of petal development. At earlier stage, the estimated g depended on the N amount. These results indicate that g changes with growth temperature and suggest that TNC accumulation must be taken into account in the estimation.     

Big-game,small-game,and gamebird hunting in New Zealand: Hunting effort,harvest, and expenditure in 1988

Abstract

A postal survey of 8639 licensed firearm owners in 1989 indicated that an estimated 117 200 ± 6300 New Zealanders (3.5% of the total population) did some hunting in 1988. An estimated 33 100 former hunters did not hunt in 1988 but thought it likely that they would hunt again in future. The survey provided useful estimates of 1988 national totals for hunting effort (4.4 million hunter days), gross expenditure ($NZ100 million), and harvest (6.5 million animals).

Small-game hunting dominated, involving 81% of hunters, 59% of total hunting effort, and 86% of total numerical harvest: rabbits (Oryctolagus cuniculus) and possums (Trichosurus vulpecula) each comprised 40% of the national bag. Gamebird hunting involved 48% of hunters, 19% of effort, and 11% of total harvest: ducks comprised 73% of the gamebird harvest. Although big-game hunting attracted the fewest hunters (42%) it ranked second for hunting effort (21%). Big game formed 3% of the total numerical harvest: pigs (Sus scrofa), goats (Capra hircus), and red deer (Cervus elaphus scoticus) were the most commonly taken. Big-game were estimated to comprise 49% of total harvest biomass, followed by small-game (47%), and gamebirds (4%). Most deer (nearly 60%) were taken for recreation, with helicopter-based hunting accounting for only one-third the total deer harvest.

A quarter of those people hunting in 1988 hunted on five or fewer days that year, and a relatively small group of mainly professional hunters accounted for a disproportionately large share of the overall harvest Hunters reported spending an average of $851 each on hunting in 1988. Expenditure on big-game comprised 44% of the total, small-game 23%, and gamebirds 33%. Expenditure per animal harvested or per day hunted was greater for big-game animals (other than goats) than for gamebirds, which were more expensive to hunt than small-game. Total hunting effort was inversely related to the average expenditure per animal harvested, regardless of the type of game.     

Hunt sightings as a tool for monitoring the distribution and abundance of brown hare <Emphasis Type="Italic">Lepus europaeus</Emphasis> in UK agricultural landscapes

We examined the potential of hare sightings data, collected during hunts by the Association of Masters of Harriers and Beagles, as a possible monitoring tool for the European brown hare Lepus europaeus. The relationship between land use and both temporal trends, and spatial patterns, in brown hare sightings across England and Wales was examined using data collected between the 1985/86 and 2004/05 hunting seasons. Hare sightings increased significantly during this period, with an average increase of 2.81 hare sightings per hunting day across all hunts since 1985. Sightings were more frequent in eastern England, where arable land is abundant, than in the rest of England and Wales which is predominantly pastoral. There was no correlation between temporal trends in hare sightings and land use change. Patterns observed using the hunt sighting data are similar to those reported by other concurrent studies that used different methods. We conclude that hunt sightings could contribute useful data to a national monitoring scheme.     

Seasonal abundance, reproduction and hunting of common quail Coturnix coturnix in the Eastern Cape Province, South Africa

This study investigated the potential overlap between breeding and hunting seasons for a population of common quail Coturnix coturnix in the Alexandria District. Seasonal abundance (assessed as the number of birds flushed per unit effort), sex ratios and reproductive condition (based on gonad sizes) of the quail were measured over a period of 16 months, including two hunting seasons. Hunting impacts were assessed in terms of the number of birds killed per unit of hunting effort. Quail exhibited a spring peak in abundance and reproduction, which coincided with the legal hunting season, and bird numbers varied markedly between years. Sex ratio varied, with males dominating early in spring. Hunters killed nearly 60% of the birds flushed, and hunter efficiency was positively correlated with the abundance of quail. These results confirm the dilemma for managers, as quail are currently hunted during the main breeding season and offtakes are high. The development of management strategies is hampered by a lack of understanding of the population biology and ecology, and impacts of hunting. A number of possible hunting strategies are discussed. Since current harvests may not be sustainable, further research is necessary.     

Cooperative Hunting and its Relationship to Foraging Success and Prey Size in an Avian Predator

Aplomado falcons (Falco femoralis) often hunt in pairs when chasing birds; 29% of 349 hunts observed in eastern Mexico involved mated pairs of falcons simultaneously chasing the same prey animal; and 66% of 100 hunts of birds were tandem pursuits. Although true cooperative hunting is uncommon in birds of prey, hunts by pairs of Aplomado falcons consistently showed signs of cooperative behavior such as use of a simple coordinative signal, and some division of labor between participating individuals. Pairs were more than twice as successful as solo falcons hunting birds (44% vs. 19%), however, there was no evidence that cooperative hunting increased the range of feasible prey sizes. The frequent use of cooperative foraging in this and similar species may relate to necessities of efficient nest defense, and food and nest procurement in savannas inhabited by a diversity of nest-site predators.     

Prioritizing the world's islands for vertebrate-eradication programmes

In the last 400 years, more species have become extinct on small islands than on continents. Yet, scant attention has hitherto been paid to prioritizing island restorations. Nevertheless, considerable conservation effort is now devoted to removing a major cause of these extinctions – invasive alien vertebrates. Because modern techniques allow the clearance of invasive vertebrates from quite large islands (up to 1000 km²), many islands are candidates for restoration. A robust strategy for allocating available funds is urgently needed. It requires, for each candidate island, an objective estimation of conservation gain and a method for predicting its financial cost. Our earlier work showed that a good first-pass estimate of vertebrate eradication costs can be made using just island area and target species. Costs increase with island area, while rodents are more expensive per unit area than ungulates. Here, we develop a method for assessing the conservation benefit of a proposed eradication and apply the method to threatened birds, but not other taxa. The method, combining information on how threatened a species is, on the impact of alien vertebrates on that species and on the islands on which the species occurs, allows us to present a means of determining which islands yield the greatest conservation benefit per unit of expenditure on vertebrate eradication. In general, although greater overall benefit would accrue to birds from eradication of invasive vertebrates on larger islands, benefit per unit of expenditure is the highest on relatively small islands, and we identify those that should be priority targets for future eradications. Crucially, this quantitative assessment provides considerable efficiency gains over more opportunistic targeting of islands. The method could be adapted to prioritize islands on a regional or national basis, or with different conservation gains in mind.     

Eradication of cats (Felis catus) from subantarctic Macquarie Island

The feral Cat (Felis catus) population on Macquarie Island was targeted for eradication between 1996 and 2002, with 761 cats captured during this period. After 22 years of cat control from 1974 integrated with control programmes for other pests, effort intensified for 2 years before a dedicated eradication programme began in 1998. The primary knock‐down for the eradication used cage trapping and shooting, with most surviving cats captured with leg‐hold traps. A total of 6298 field days and 216 574 trap nights were recorded in this operation. Factors contributing to the success of the programme included extensive planning, increased staff numbers at critical times, better access to remote areas of the island, introduction of leg‐hold traps, sufficient operational funding and good collaboration between government agencies operating on the island. The programme would have benefited from earlier deployment of detector dogs and better posteradication monitoring of a broader range of native species impacted by cats. The successful eradication of cats from Macquarie Island, being the second largest achieved to date, provides valuable experience for cat eradication attempts on other large remote islands. This programme relied on ground‐based techniques with minimal use of poisons and provides possible options for sites where broad‐scale poisoning, or where aerial distribution of poisons, cannot be used.