NB: The information in this case study has been extracted from Fraser Parkes and Thomson (2003) unless otherwise stated.
1. 0 Management Strategies
1.1 Eradication of Newly Escaped Deer Populations
In New Zealand various species of deer, mainly red deer (C. elaphus scoticus) have established themselves in the wild, including areas of Northland and Taranaki. One study (Fraser Parkes and Thomson 2003) has found that in 85% of cases of farm escape of deer either farmers or the Department of Conservation successfully recaptured deer. Eradication of wild deer populations (following farm escapes) has been carried out in Northland and Taranaki between 1997 and 2000 and it is suggested such management should be extended to deer-free areas north of Auckland, the Coromandel Peninsula and Banks Peninsula. To know more eradication campaigns in Northland and Taranaki (including costing details) please see Fraser Parkes and Thomson (2003) Management of New Deer Populations in Northland and Taranaki.
Farm escapes of deer in New Zealand are usually the result of inadequate fencing or damage to adequate fencing. Relevant legislation on the keeping of deer and deer fencing regulations is in place. Deer farming is prohibited in certain parts of New Zealand and, where it is permitted, farming and fencing standards are regulated under the Wild Animal Control Act 1977, particularly section 12, which requires farmers to obtain a permit to farm and to maintain adequate fences. DOC is developing more comprehensive standards andinspection procedures that will be a prerequisite for farmers to obtain approval to farm deer, and act as a guide to DOC officers, especially when inspecting areas where escaped deer pose additional risks.
Illegal liberations of deer also pose a problem and there may need to be enforcement of the relevant legislation to discourage people from liberating deer (although this has reported to be a problem with sika deer not red deer per say).
1.3 Pest Management Strategies
Finally, public and stakeholder awareness of the problem is reinforced in proactive planning documents such as the local Conservation Management Strategies and Regional Pest Management Strategies. Reactive management, aimed at dealing with new deer populations as they are discovered, has focused on surveillance, early detection, and on eradicating any populations discovered.
1.4 Freecall Number
In Northland, DOC has a toll-free number (0800 FIND DEER), which farmers use to report deer escapes to the department. Typically, DOC Northland receives about four calls each month and checks the reports within 24 hours. This system has already resulted in the successful recapture of several mass deer escapes. It encourages farmers to report early and not just rely on their own devices, and is visible evidence that management agencies are taking the problem seriously.
The usual method in New Zealand is to use randomly located faecal pellet transects (Baddeley 1985, in Fraser Parkes and Thomson 2003), but in the case of low-density and/or patchy new deer populations a stratified design is recommended, i.e. more transects would be located in areas known or suspected to have most deer.
2.2 Detecting Deer
This can be done via information from the public (reportings of sightings), searching for visual signs in the field (feacal remains, browsing signs and tracks), spotlighting, aerial surveys and use of dogs and trained experts or thermal infrared cameras. Surveying methods are further discussed in Fraser Parkes and Thomson (2003).
3.0 Control Techniques
3.1 Hunting Deer
Many ungulate populations have been eradicated from New Zealand (Parkes 1990, unpubl. data, in Fraser Parkes and Thomson 2003) and in nearly all cases this was achieved finally through various forms of ground hunting. Aerial hunting is another well-developed control method for ungulates in New Zealand, and is commonly used to harvest deer for game meat (Challies 1990; Parkes et al. 1996). Although this method is most successful in non-forested habitats, it is often possible to shoot animals in forests either through the canopy or when the animals are crossing slips, river terraces, or other open habitats.
Team hunting is one way to decrease the proportion of animals that escape their first encounter with the hunters. It was trialed against deer and chamois in the South Island in the 1950s (Batcheler and Logan 1963, in Fraser Parkes and Thomson 2003), but has improved considerably in recent years in campaigns against feral goats with the use of dogs (trained for the purpose) and the availability of radio communication devices to keep the hunters in contact one with another (Parkes et al. in press, in Fraser Parkes and Thomson 2003).
3.2 Poisoning Deer
Deer can be poisoned by aerial baiting (Daniel 1965, in Fraser Parkes and Thomson 2003). Between 30% and 93% of deer are usually killed during aerial 1080-baiting campaigns aimed at possums (Fraser and Sweetapple 2000, Nugent et al. 2001a, in Fraser Parkes and Thomson 2003). Widespread application of 1080 baits is expensive, but the may be of use in eliminating localised populations of deer that are not easily killed by other means. The use of 1080 gels smeared on leaves of palatable plant species as baits has successfully reduced a moderate-density red deer population in the central North Island by 78% (Sweetapple 1997, in Fraser Parkes and Thomson 2003). It is likely to be less successful in low density populations with abundant food sources, as evidenced by the failed attempt to eradicate red deer on Secretary Island (New Zealand) (Tustin 1977, in Fraser Parkes and Thomson 2003).
3.3 Exclusion Fencing
Duncan and colleagues (2006) found that fencing (in comparison to either form of hunting; aerial or ground) is the most effective deer control method of encouraging mountain beech seedling growth and mountain beech forest recovery rate. The same may apply to other forest ecosystems. The use of fencing may prove to be useful in preventing the re-invasion of deer into ecologically sensitive areas following deer eradication or control.
4.0 Integrated Management
The proposed eradication of red deer from Secretary Island (New Zealand) is designed to protect the ecological values of the island, and to test and develop methods for intensive control of deer (Crouchley et al. 2007). The eradication campaign will involve a combination of control methods including aerial hunting, ground hunting, use of barrier fences and capture pens, use of self-attaching radio transmitter collars and ground baiting (1080 gel).As there has never been a deer eradication campaign on an island of similar size or habitat this project is somewhat experimental and will be a valuable lesson in vertebrate management and island eradications. For the details of this integrated management proposal please see Crouchley et al. 2007. Secretary Island Secretary Island Operational Plan: Deer Eradication.
Duncan and colleagues (2006) performed an analysis of the mountain beech (Northofagus solandri var. cliffortioides) data from Kaweka Forest Park to guide managers on future deer control. They assessed the recruitment rate of mountain beech forest under three forms of deer control (deer-fenced plots, aerial hunting areas and recreational hunting areas). Mountain beech seedling growth, recruitment and survival were monitored to under the three conditions and then modelled to determine recovery rates. The models indicated that mountain beech forest would take the longest time to recover under recreational hunting and the fastest time to recover under fencing (an up to 80 year shorter time period compared with recreational hunting).
There is currently great interest in restoring ecosystems affected by invasive organisms. While government agencies in New Zealand have attempted to reduce deer numbers and restore forests to something approaching their pre-invasion composition and structure, they have met with only limited success. Coomes and colleagues (2003) have investigated and discussed the various fascinating dynamics that are involved in forest regeneration following deer control. Based on a literature review, the authors identified the following factors (some inter-related) which could impact forest regeneration and make deer impacts irreversible: (1) palatable species remain highly browsed even at low deer densities as a result of diet switching; (2) vacated niches become occupied by plant species not eaten by deer; (3) seed sources become locally extinct; (4) successional pathways become fundamentally altered; (5) ecosystem processes shift; (6) other exotic animals and/or plants become naturalised and weaken the effectiveness of single-species (deer) control. On a positive note scientific research can contribute to effective forest restoration by the creation of empirically based forest-dynamics models (eg: computer simulations) that place regeneration in the context of other processes such as disturbance, soil fertility, and multiple invasive organisms (Coomes et al. 2003).
5.2 Other Research
The Department of Conservation (New Zealand) is currently involved in trialing various control technologies which could potentially be incorporated into deer control stategies. These include: (i) remote monitoring of capture pens, (ii) self-attaching transmittor collars, (iii) use of baits and/or lures, monitoring cameras, (iv) night vision equipment and (v) DNA analysis of hair samples (Crouchley et al. 2007).
Crouchley, D., Brown, D., Edge, K. and McMurtrie, P. 2007. Secretary Island Secretary Island Operational Plan: Deer Eradication. Department of Conservation: Te Anau. [Accessed 23 March 2007, from: http://www.doc.govt.nz/templates/MultiPageDocumentTOC.aspx?id=43013]
Coomes, D.A., Allen, R.B., Forsyth, D.M. and Lee, W.G. 2003. Factors Preventing the Recovery of New Zealand Forests Following Control of Invasive Deer, Conservation Biology 17 (2): 450–459. [Accessed 23 March 2007, from http://www.blackwell-synergy.com/doi/abs/10.1046/j.1523-1739.2003.15099.x]
Duncan, R., Ruscoe, W., Richardson, S. and Allen, R. 2006. Consequences of Deer Control for Kaweka Mountain Beech Forest Dynamics (Landcare Research Contract Report: LC0607/021). [Accessed 23 March 2007, from: http://www.doc.govt.nz/upload/documents/conservation/threats-and-impacts/animal-pests/kaweka-deer-control.pdf]
Fraser, K.W., Parkes, J.P. and Thomson, C. 2003. Management of New Deer Populations in Northland and Taranaki, Science for Conservation 212. [Accessed 22 March 2007, from: http://www.doc.govt.nz/upload/documents/science-and-technical/SFC212.pdf]