Trialling of a bird repellent to prevent kea strike on sheep

Project Background

Conflict between kea and New Zealand high country sheep is an on-going issue which prior to protection being granted to kea in the early 1970’s resulted in an estimated 150,000 kea killed in a legal bounty system. The bounty was initiated due to kea attacks on sheep resulting in high stock losses (Temple, 2011). The term ‘flagging’ is used to describe how the tuft of wool is pulled so that it stands above the rest of the fleece. The term ‘kea strike’ is used to indicate physical damage done by a kea to sheep.

Kea strike may be more specifically defined as trauma to the back or flank of a sheep caused by a keas beak digging through fleece, hide and flesh in an attempt to locate high energy fat (particularly around the sheep’s kidney area). Sheep may die from the resulting injury either directly or indirectly depending on the extent of the attack. Sheep may die from direct physical trauma, subsequent blood poisoning (if sheep are unvaccinated), or through physical trauma while trying to escape an attack.

Flagging of sheep may occur wherever South Island high country sheep farms overlap with kea habitat; essentially along the length and breadth of the Southern Alps (mountains and ranges). Incidence of kea strike appears linked to the following husbandry related factors: length of wool, sheep breed, presence of sheep carcasses, vaccination and booster application and altitude of stock during winter (Lawrence, 2010). Farms neighbouring each other, each with different sheep husbandry routines which involve the latter two factors in particular, appear to have very different experiences with prevalence of kea strike.

Additional contributing factors may be farm location in relation to kea habitat, and individual and learned behaviour of resident birds. Kea strike is often attributed to a few “rogue” kea (potentially males) however removal of these birds in the past has not necessarily resulted in the removal of the problem. Kea are highly opportunistic, curious and intelligent and may learn by imitation and/or presence of sheep carcasses left on hills by farmers which they learn are a source of high energy food (Lawrence, 2010). Additionally kea strike may be an evolutionary response to a harsh environment. Evidence of kea damage to the same area in moa remains has been suggested (Wilson, 2004) and as such removal of moa by Maori and subsequent introduction of sheep by Europeans may unintentionally have provided a new food source to fill a human induced void.

Evidence of kea strike

The majority of kea strike evidence in the 1800’s – through until the 1990’s was anecdotal. Photos and drawings describing wounds on the backs of sheep were often attributed to kea during this time. First hand witness accounts were documented by Benham (1906) in the mid – late 1800’s while Alfred Wallace in 1889 attributed this behaviour to behavioural adaptation. Wallace stated at that time, “As a natural consequence, the bird is being destroyed as rapidly as possible, and one of the rare and curious members of the New Zealand fauna will no doubt shortly cease to exist”. The first documented film evidence of kea attacking sheep was by Natural History New Zealand (NHNZ) in 1993 which showed kea riding and attacking snowbound sheep at night (NHNZ, 2006) on Invincible Spur in the Rees Valley, August 1992 (Iris Scott, pers comm).

Historical Solutions

In an effort to “fix” the kea problem on high country runs, the government instigated a bounty system for kea. Bounties reached as high as £1 a beak - about $120 today (Temple, 2011). Half of the bounty amount was paid out by the Department of Agriculture who published this information and from this a conservative figure of 150,000 keas were estimated killed in the 100 years to 1970 (ibid).

There are now fewer than 5,000 kea estimated remaining across the entire range and in at least one area under study, a population once considered to be a model of stability, has declined by 80% over a 10 year period from unknown causes (KCT, 2011).

Today illegal poisoning and shooting incidents continue to be reported in high country areas and in some cases birds have been shot legally or removed by DOC to stop rogue birds attacking sheep. Removal of adult males from the population in this way is of particular concern as stated by Elliott and Kemp (1999);“A decrease in adult survivorship will cause a much more rapid decline than any other parameter”. Kea nest from June – December and removal of males who may be feeding females and their chicks may result in a failed breeding attempt that year and/or death of chicks and possible loss of breeding years while the adult female finds a new mate in subsequent years.

Additionally there may be an inadvertent selection process with removal of important investigative behavioural characteristics from the wild kea population.

As such, it is imperative that a long-term, sustainable solution to this historical issue, which benefits both run holder (and their stock) and kea is urgently found.

2014 Trials

The second off our trials, commenced on the 6 May 2014 on a flock of mixed sex rising two year old Merino and Perendale sheep. Of the 601 sheep in the trial 375 sheep were Merino and 226 were Perendale. Of these 140 Merino (37%) and 115 Perendale (51%) were treated and the remaining 346 sheep were untreated (control).

All trial sheep were checked for signs of kea injury. No sheep in the trial had previous sign of kea flagging.

All treatment and non–treatment sheep will be individually inspected for signs of kea strike (flagging or drilling) at or around the beginning of June. Data and photos will be collected for all the animals in the trial and wool samples will be taken from six selected sheep that received the treatment.

Four standard DOC acoustic recorders were set adjacent to the area where the trial sheep will be grazed over the next month to ascertain presence of kea. Each recorder is set to record 10 hours per day between 2000 hours and 0600 hours.

2012 Trials

Funded by Cincinnati Zoo and Botanical Gardens

Trialling of the secondary bird repellent anthraquinone (AQ) took place at sheep station in the Wakatipu area during the spring of 2011 (16 Sept – 7 November) and winter of 2012 (31 May – 18 July). Timing of these trials was dependant on observed kea visitations by farmer, communications by farm manager, and access (weather conditions). It was hoped that these trials would continue during the winter of 2013, however this did not eventuate due to issues with all of the above.

During spring 2011, a sheep carcass was placed in an area of historical kea strike and monitored by motion sensor camera for evidence of kea interaction. No kea were observed interacting with the carcass and no kea strike events were recorded by the farm during this time. It was considered too late in the season and as such full trials were scheduled for winter 2012.

The 2012 trial was conducted on a flock of 337 mixed sex rising two year old merino sheep; 203 of which were treated with the AQ/lanolin mix and the remaining 134 were untreated (control). A total of 341 sheep were mustered up and examined 45 days later. Of these, 197 were treated – 15 of which showed signs of kea strike (7.6%) and 144 were likely untreated – 4 of which had signs of kea strike (2.8%). This amounted to a total of 10.4% sheep showing some evidence of flagging by kea. No animals died as a result. Review of acoustic recorder data found that kea were present for at least some of this and subsequent periods. The majority of vocalisations occurred in the early hours of the morning (around 2am).

Although there were no deaths and minimal kea strike, results to date are inconclusive and additional trials will need to be conducted to increase sample size. As such an additional trial site which has the ability for more control is being investigated for winter 2014.


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