TECHNIQUE

Tracking Erinaceus europaeus - West European Hedgehog (Mammal Husbandry & Management)

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Summary Information
Type of technique Health & Management / Hedgehogs: Health & Management / Techniques:
Synonyms and Keywords See also: Marking Hedgehogs (Erinaceus europaeus)(Techniques)
Description This page has been prepared for the "Hedgehogs: Health and Management" Wildpro volume, and is designed for the needs of the following species: Erinaceus europaeus - West European Hedgehog

Radio Transmitters:

  • Radio-transmitters can be used to allow hedgehogs to be tracked for long periods of time.
  • The transmitter is usually glued onto the spines either directly  (using a fast-drying glue e.g. epoxy resin) or via a piece of Velcro.
    • Harnesses have been used in the past but tended to chafe and interfere with the hedgehog's ability to roll up.
  • A special aerial is required to detect the transmitter and practice is needed to use one effectively
  • Luminescent tags or paint can assist in precise location in the dark while minimising close approach and therefore disturbance of the hedgehog..

Spool-and-line

  • A small spool of thread can be attached to a hedgehog by gluing it to the spines.
  • One end is left free on the ground and the hedgehog is released.
  • The thread unwinds as the hedgehog travels, allowing an accurate path to be marked.
  • The system is only useful for relatively short distances (until the thread runs out).
Appropriate Use (?)
  • Research into hedgehog movements and home ranges relies on mark-recapture and radio-tracking studies. (B228.4.w4) 
  • Spool-and-line tracking can be used to investigate habitat selection and foraging strategy of individual hedgehogs. 
    • The pattern in which the line fell was useful in determining whether the hedgehog stopped in an area to forage (jumbled mass of string on dung heaps rich in invertebrates) or travelled straight through (straight line of string). (P35.4.w8)
    • The study concluded that spool-and-line technique was useful in providing a detailed path of hedgehog movements over a small area with more detailed information generated than from radio-tracking. However the length of the line limited the area over which the study could be performed, making investigation of home range sizes impossible. (P35.4.w8)
  • Marking-recapture surveys and techniques for tracking (e.g. line-and-spool, beta-lights, radio-telemetry) have been used to investigate the impact of the introduced hedgehog population on the resident wading bird populations in the Uists, Outer Hebrides, Scotland. (P35.3.w10)
Notes
  • Recent radio-tracking studies have successfully used glue to secure transmitters to the spines of hedgehogs over their dorsum. (B228.4.w4, B254.18.w18)
  • A compromise exists between the design of transmitter aerials and potential adverse effects on the study animals. (B228.4.w4)
    • 'Whip antennae' or 'trailing wires' may enable monitoring over a large range but may become entangled in vegetation, thereby restricting the hedgehog. (B228.4.w4)
    • 'Integral aerials' (e.g. iron-dust rod) do not risk entanglement. They have no external connections which might break or allow water to enter the transmitter. However they may weigh more than an external antenna and they perform less well than a whip antenna. (B228.4.w4)
  • Future developments in transmitter design may lead to lighter unit weight, reduced power requirements and potential for remote telemetry of physiological variables (e.g. body temperature, heart rate). (B228.4.w4)
  • Temporary luminous transmitter tags detected from a distance by deep red torch light have been employed to minimise disturbance to study animals during tracking studies. (B228.4.w4, J147.2.w1) See: Marking Hedgehogs (Erinaceus europaeus) (Techniques)
  • Distance ranges for reception of signals during radio-tracking study range from 100 yards using early home made devices to 1000 yards with modern equipment. (B254.18.w18, J147.3.w1, P17.49.w1)
  • Transmitters should be designed to be of minimum mass. (B228.4.w4)
  • The weight of transmitters used for surveys of  hedgehogs in the literature mainly range between 12 and 28 g although use of devices weighing between 30 and 40 g has been reported.(B228.4.w4)
  • Batteries designed for 'deaf-aids' have been used to supply power for transmitters and can be replaced via thread systems without the need to remove the unit from the hedgehog.(B254.18.w18)
  • Modern transmitters allow small battery size, higher performance than older designs, and remote telemetry. [2004](V.w57)
    • Complete radiotracking tags, including battery and antenna, are now available down to weights as low as 0.35 g, while battery life available for lightweight tags is longer than it used to be. [2004 data](W492.Feb04.w1)
  • Public cooperation is important for radio tracking studies in inhabited areas involving gardens etc. (J147.2.w1)
Complications/ Limitations / Risk
  • Radio-tracking is difficult in suburban fragmented habitats because of signal distortion and problems with land access e.g. walls, private areas. (B254.18.w18)
  • Direct observation of hedgehogs during radio-tracking studies may not be possible when study animals enter areas of land which are restricted/ private access. In this instance, 'triangulated fixes' which are subject to error must be used. (B228.4.w4)
  • Radio-transmitter design must be appropriate for use in the hedgehog. Attachment of the transmitter using a collar or band design is not generally practical in this species since the neck and waist of the hedgehog are poorly defined and the small tail tapering in profile. (B228.4.w4)
  • Early radio-tracking studies used a flexible harness made of elastic or silicone rubber tubing to attach the transmitter to the hedgehog. Whilst the harness still allowed the animal to roll-up for defence, some constraint of their movement may have resulted. (B228.4.w4, B254.18.w18)
  • After a month or so natural shedding of spines may loosen the transmitter; if not either re-glued or removed it may pull off, occasionally causing a slight wound. (P17.49.w1)
  • The electrical components of transmitters must be housed within waterproof resin. (B228.4.w4)
  • Battery weight within the transmitter may be quite high in order to supply sufficient delivery and power. [1994 data](B228.4.w4)
  • Modern transmitters allow small battery size, higher performance than older designs and remote telemetry. [2004](V.w57)
    • Complete radiotracking tags, including battery and antenna, are now available down to weights as low as 0.35 g, while battery life available for lightweight tags is longer than it used to be. [2004 data](W492.Feb04.w1)
  • Consideration should be given to the possibility that carrying a transmitter may alter hedgehog behaviour, perhaps affecting results of a scientific study. (B228.4.w4)
    • Reports of complications associated with transmitter use in hedgehogs are infrequent; no effect on body condition in relation to transmitter use was noted in one study. However transmitters on individual study hedgehogs have become entangled in grass on two occasions. (B228.4.w4)
      • In one study involving eight rehabilitated and released hedgehogs one animal was found with the transmitter snagged on grass and brambles; it was rescued and re-released. (J147.2.w1)
    • The frequency and level of disturbance of hedgehogs varies between radio-tracking studies. (B228.4.w4)
  • The relatively short length of the line used in spool-and-line tracking limits the area over which a study could be performed, making investigation of home range sizes impossible. (P35.4.w8)
Equipment / Chemicals required and Suppliers
  • Appropriate transmitters (with power source) and receiver.
Expertise level / Ease of Use
  • Experience and training are required to effectively track an animal using a transmitter.
Cost/ Availability
  • It can be relatively simple to make home-made transmitters for use with hedgehogs at minimal expense however receivers are more expensive. (B254.18.w18)
  • Transmitters and receivers are available from specialist companies, e.g. Biotrack Ltd.
Legal and Ethical Considerations
  • Transmitters used for tracking hedgehogs must be designed to minimise interference with the behaviour of the tagged individual and not to compromise its well-being or affect its chances of being predated. 
  • Transmission frequencies used for monitoring must be high to avoid interference with radio or police communication frequencies according to the Wireless and Telegraphy Act 1949. Special adaptation of normal transistor radios is required for reception of these frequency signals. (B254.18.w18)
  • See: Wildlife Casualty Legislation (with special reference to UK Wildlife): Marking of Animals and other Research 
Author Debra Bourne (V.w5)
Referee Becki Lawson (V.w26) and Suzanne I. Boardman (V.w6)
References B228.4.w4, B254.18.w18, J147.2.w1, P35.3.w5, P17.49.w1, P35.3.w10, P35.4.w8, W492.Feb04.w1, V.w57

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