Rodent control

Barn Owl Trust
Waterleat, Ashburton
Devon TQ13 7HU
Rodent Control
Tel: 01364 653026 email [email protected] This leaflet provides information on
rodenticide on wild Barn Owls. There is a concern minimising the risks to Barn Owls whilst
that it may affect hunting efficiency and breeding controlling mice and rats. It lists rodenticide
success. Monitoring of Barn Owl carcasses has products, indicating which ones are less likely
shown an increase in secondary poisoning; the percentage of carcasses containing residues of to kill Barn Owls and a non-toxic product
second-generation rodenticides increased from 5% which is now available.
in 1983-4 to 53% in 2003 (Predatory Bird Monitoring Scheme). In 2006 a new, more sensitive method of Background
analysis was used. This revealed that 63% of the British Barn Owls mainly hunt over agricultural land but also hunt around farm buildings - particularly in winter. generation poison in their livers. Had the old method Rodents, especially rats, can be a serious problem on been used, the poison would have been detected in farms and tend to inhabit buildings used for feed, bales, just 39%. While this shows that levels of poisoning or livestock. The number of rodents in and around farm have gone down since the high of 2003, it also buildings increases during the breeding season (in the suggests that previous levels have been significantly summer) and during autumn extra animals often move underestimated. What the 2003 figure would have in from hedgerows and watercourses. Traditionally, been had the new method been available then can wintering Barn Owls hunted within farm buildings and only be guessed at. The figure for 2007/2008, again helped to keep rodent numbers down. This also maximised the owls’ chances of surviving periods of severe winter weather. As farm hygiene improved the use of rodenticides (poisons to kill rodents) became In cases of rodenticide poisoning of non-target animals, common. These days about 90% of farms use them. take the victim to a vet immediately for an injection of vitamin K1. For a poisoned Barn Owl, daily injections Rodenticide bait usually takes the form of grain or for 5 to 7 days are recommended (note: there is no pellets to which the poison has been applied, and is specific antidote to alphachlorolose or calciferol). If you often coloured blue. There are lots of brands available find a dead Barn Owl or indeed any animal and with various chemical ingredients (see Tables 1, 2 and poisoning is suspected, please telephone DEFRA 3). They are normally supplied loose, in small boxes immediately on 0800 321600 to report the incident. for the rodents to enter, or in small bags (scatter- packs) and are incorporated into bale stacks, etc. Exposure to the risk of secondary poisoning is both There is also a product now available that is not a
frequent and widespread. The original first generation poison but a plant-based product that kills by
types such as Warfarin (Table 1) have been upsetting the digestive system of rats and mice and
superseded by second-generation poisons (Table 2) is apparently harmless to other animals. Please
because rats in some areas became Warfarin resistant. see the information box entitled Eradibait.
Due to their foraging behaviour, Barn Owls along with Red Kites and Kestrels are far more likely to suffer How the poisons work
secondary poisoning than any other species. Most rodenticides are anti-coagulants - they prevent the blood from clotting and thin it until the victim All rodenticides listed in the tables overleaf are toxic eventually dies from internal bleeding. The time taken and can kill Barn Owls. However, the instructions for a rodent to die after eating the bait varies from two provided on rodenticide product containers do not to twelve days. A rodent eating a sub-lethal dose (not mention the risks or explain the mechanism of enough to kill it) may carry the poison in its liver for secondary poisoning in spite of the fact that these are several months. Before a poisoned rodent dies it may well known to the manufacturers and the government be caught by a Barn Owl which then ingests the who licence the products. Instructions are given to keep poison - this is called secondary poisoning. Creatures the bait covered up in order to protect non-target which have been killed by secondary poisoning include species, but this does nothing to reduce the risk of Barn Owls, Tawny Owls and foxes. Animals which have secondary poisoning. Recent efforts by the rodenticide been killed by directly eating rodenticide baits include industry to tackle misuse and the inclusion of the words dogs, cats, pigeons and blackbirds (DEFRA). “Harmful to Wildlife” on product labels is certainly a step in the right direction. However, it is important for all Research has shown that poisoned Barn Owls either rodenticide users to be aware that secondary poisoning die slowly or survive and carry a residue of poison in cannot be completely prevented no matter how the their bodies. Typically it takes 6 to 17 days for a Barn poisons are deployed. The approved use of rodenticide Owl to die after eating three mice containing products (that follow the manufacturer’s instructions) Brodifacoum. Unfortunately no research has been cannot possibly prevent poisoned rodents being caught carried out on the effects of a sub-lethal dose of Barn Owl Trust - Conserving the Barn Owl and its Environment
First Generation Poisons - to be used in areas

Table 2 continued….
where rats demonstrate little resistance to these chemicals. Chemical
Product names
Manufacturer
Killgerm Sewercide, Killgerm Chemicals Ltd Sakarat Bromabait Killgerm Chemicals Ltd Second-generation Poisons - to be avoided on
farms where Barn Owls are known to be present within Chemical
Product names
Manufacturer
Brodifacoum Paste Rentokil Initial UK Ltd Jaguar Rodenticide, Bell Laboratories Inc Bromard, Bromotrol, Rentokil Initial UK Ltd See next page for a Non-Toxic product!
Barn Owl Trust - Conserving the Barn Owl and its Environment
Other poisons - to be avoided on farms where
Eradibait
Also sold as -
Growing Success Rat & Mouse Killer
Chemical
Product names
Manufacturer
NON-TOXIC PRODUCTS
þMade entirely of food-grade natural vegetable materials with NO added toxins or artificial chemicals. þHighly effective against rats and mice (when used properly) and apparently safe for other species. Deerat Concentrate Rentokil Initial UK Ltd For more information and a list of suppliers please visit www.eradibait.com or phone the distributors 01673 885175
References
Incidents of secondary poisoning can be reduced by adopting more sympathetic methods of rodent control. Pesticide Poisoning of Animals: Investigations of The Barn Owl Trust is now recommending a new Suspected Incidents in the United Kingdom. (Annual product which is apparently effective against rats and Publication - Various Authors and Years). DEFRA. mice and completely non-toxic to other animals and Natrocell Technologies information pack. 2001. birds (see information box). If you have a rodent problem, please consider the following suggestions: Newton, I., Wyllie, I. & Freestone, P. 1990.
1. Find the rodents' source of food and prevent their Newton, I., Shore, R.F., Wyllie, I., J.D.S. & Dale, L. 1999. Empirical evidence of side-effects of 2. Remove their hiding places, block access holes rodenticides on some predatory birds and mammals. with stone or balls of squashed wire netting. Pp. 347-367 in ‘Advances in vertebrate pest 3. Use non-toxic products such as Eradibait (see box) management’, eds. D.P. Cowland & C.J. Feare. Fürth, or alternative methods of killing such as traps, cats, Ramsden, D. 1998. Effect of Barn Conversions on 4. If you must use poison, choose one containing local populations of Barn Owl. Bird Study 45, pp68-76. Warfarin or another first-generation poison as these are less likely to cause secondary poisoning Walker, L.A. et al. 2007. Wildlife and pollution: than a second-generation rodenticide. To find out if 2005/06 Annual Report. JNCC: Peterborough. rats in your area are resistant to first-generation rodenticides visit: www.bpca.org.uk/microsite.asp?site=1113&pageid=8 Acknowledgements
We would like to thank Alan Buckle, chairman for the
5. Put down the bait for a maximum of five weeks and Campaign for Responsible Rodenticide Use (CRRU) for his remove it after this time or sooner if the rodent help in the revision of this leaflet. Further information on wildlife and rodenticide use can be found at www.
6. Current disposal guidelines given by The Health Barn Owl Trust 1989
and Safety Executive are as follows: Search for Latest revision 2011
and remove rodent bodies at frequent* intervals during treatment. Collect and dispose of the The Barn Owl Trust is a registered charity dedicated to remains of bait and any remaining rodent bodies the conservation of the Barn Owl and its environment. after treatment. All waste should be double-bagged You can become a Friend of the Barn Owl Trust and
using bin liners or similar before disposal in a bin support our work by making a regular donation. Friends
with a secure lid to prevent accidental poisoning of receive our biannual magazine Feedback, our Annual dogs, cats, birds, foxes and other wildlife or by contacting either a specialist contractor or the Local Authority where waste bins are not provided. Do The Trust provides a wide range of free leaflets on Barn not dispose in any other way. (*Intervals will vary Owl related matters. For details of these and further depending on product used; see manufacturer’s information about the Trust and its work, please write including a large SAE to the Barn Owl Trust, Waterleat, 7. Rodenticides are designed to kill. Treat any statement that products can be "safely" used with Email: [email protected] Web: www.barnowltrust.org.uk Barn Owl Trust - Conserving the Barn Owl and its Environment

Source: http://barnowldemo.dnadigital.co.uk/content_images/pdf/Rodent_Control_21.pdf