Technical Note: Breakaway and Expansion Collars

Introduction

Transmitters for mammals are often attached by utilizing a collar. Most collars have adjustment ranges that allow fitting the collar to the animal's neck girth. Once deployed, however, the collar circumference remains fixed. Some collar materials, such as leather, tend to stretch and shrink somewhat and will eventually decay. Other collar materials are much more durable, retaining their size and flexibility for many years under a variety of conditions.

Some applications require collars that expand and/or breakaway.

• Expandable collars are designed to allow for growth in young animals, neck expansion of male ungulates during rut, or seasonal changes in neck size such as when bears gain weight in the fall.
• Sometimes collar expansion is not necessary, but there is a desire to have collars fall off the animal or breakaway at some time in the future.
• Combinations of the two types of collars (i.e., expandable/breakaway) are also applicable to some situations. Numerous types of expandable, breakaway, and expandable/breakaway collars have been used. Over the years, we have worked with biologists to develop different types of expandable and breakaway collars to meet specific design criteria and study goals. Because of our involvement in these developments, we are in a position to assist users of our equipment by sharing the knowledge we have gained and that contributed by other researchers.

Breakaway Collars are based on a release device that is placed on an animal -- subjected to abrasion, extreme temperatures, moisture, dirt, UV exposure, and other abuse -- yet expected to fall off according to a predetermined schedule. The release device is frequently an environmentally degradable; thus, variations in the environment between years or areas can result in variation in retention times for the collars. Electronic timers which time and then trigger breakaway are occasionally suggested, and can be reliably constructed at a modest increase in cost and weight. However, the electronics still must trigger the actual separation device. A pin must be pulled, clasp released, or material severed; thus, the mechanical problems associated with freezing, dirt, jamming, etc. remain. Radio-link breakaways are sometimes suggested; however, they also use mechanical separation devices, and are thus subject to similar abuse and failure modes. Radio-links also require that the animal be fitted with a receiver. This increases the current drain on the power supply, increases size and weight of the package carried by the animal, and decreases overall reliability of the system because of increased complexity.

Expandable Collars present another series of design challenges. Often, a first priority in the design of an expandable collar is that it expands easily enough to avoid harm to the animal. Collars designed to expand are necessarily easier for the animal to remove than a collar of fixed circumference. Collars may prematurely expand because of neck rubbing, scratching, social interactions, or even the mass of the transmitter moving as an animal runs. The use of expandable collars may increase the danger of an animal catching a foot while scratching, or stepping into the collar while feeding. Increasing resistance to expansion increases the possibility that the collar will not expand at the desired time. Reasonable success has been achieved with collars that expand as young ungulates grow. Limited work has been conducted with dexterous species such as felids, although a harness design has been used with some success. Repeated collar expansion and contraction is frequently desired for seasonal neck expansion, but such cycling is difficult to achieve because many materials and designs do not contract to original size and shape after being continuously expanded for days, weeks, or longer.

Performance Issues

Various articles have been published describing collar designs, with most of those described being at least moderately successful for the particular use described (most people do not publish failures). Our experience working with various species in a variety of environments has sometimes shown large differences in performance of a particular collar design depending on species, age, climate, habitat, and even behavior of specific populations or individuals. For example, latex tubing used as a breakaway mechanism in some collars is broken down by UV light; such collars usually do not last as long in open areas where they are exposed to large amounts of UV radiation, as they do in heavily forested areas which receive much less exposure. Likewise, the amount of diurnal versus nocturnal activity can influence retention time. Slight variations in material, threads, number of stitches, etc. can substantially impact collar performance as well.

This is not to say expandable or breakaway collars should not be used. Certainly some applications require them. Users should be aware, however, that a variation in performance is to be expected. Some collars fall off prematurely; others remain on longer than desired. The professional staff at Telonics has a pool of knowledge gained from years of experience, though we do not have all the answers. Therefore, we encourage you to share your information with us so that we may share it with others. If you have the perfect expandable collar, or a good one, or something you tried that was a miserable failure, we would like to know.

A brief description of several of the expandable and/or breakaway collars we are currently producing follows. Please contact our laboratory to discuss the specific requirements of your application prior to ordering.

Figure 1. Multiple Style Collars

CB-1, breakaway collar (see Figure 1, Collar B)
This firm, plastic collar is formed in a teardrop shape and fastened at the top with latex tubing. Inside diameter of the plastic collar is 9-10 cm; a foam lining is typically used to fit smaller necks. The foam compresses and breaks down through time, allowing for limited growth of the animal. After some period of time (typically months), the tubing decays and/or breaks allowing the collar to fall off. Longevity of the attachment is influenced partially by the tension applied to the latex tubing, and partially by environmental factors such as UV light, acid rain, etc. which in turn are influenced by geographical area, habitat type, activity periods, etc. The CB-1 has been used primarily with the MOD-300 configuration transmitter on deer and pronghorn antelope fawns.

CB-2, breakaway collar (see Figure 1, Collar D)
While similar to the CB-1, the CB-2 is a bit larger. The collar is approximately a 10 x 14 cm diameter oval, and a foam lining allows fitting to smaller necks. The CB-2 has primarily been used with the MOD-400 configuration transmitter on juvenile deer and pronghorn.

CB-3, breakaway mechanism
Our CMM or CLM collars are cut, then the two sections are reattached using latex tubing. This does not allow for neck expansion, but does provide a mechanism whereby collars eventually fall off the animal. Breakaway times are dependent upon species, climate, habitat, and physical stress or abrasion. The attachment tubing is often covered with heat shrink tubing, tape, or other material to extend the life of the attachment. The CB-3 is used primarily on collars for large mammals with MOD-400, MOD-500, and MOD-600 configuration transmitters.

CB-4, three-stage expansion/breakaway collar (see Figure 1, Collar C)
This collar is an elastic strap with three stitched folds and a breakaway tab. The folds tear out and the elastic expands as pressure is applied by the animal's neck growth. Eventually the collar is slipped over the animal's head or drops when the breakaway tab releases. Expansion and breakaway times depend upon the species and environmental variables. In addition, this design is probably more susceptible to abrasion, catching on vegetation, and other physical stresses than some other designs. The CB-4 has primarily been used with the MOD-300 configuration transmitter on species inhabiting open areas (e.g., caribou).

CB-5, expansion collar (see Figure 1, Collar A)
This collar is an elastic strap encased in a protective sleeve. The collar can be provided with adjustment holes for initial fitting to various neck sizes, and is normally designed to expand to slightly less than two times the size at deployment. Eventual degradation and loss are caused by physical stress and UV breakdown. Modified versions have been used with the MOD-300, MOD-400, and MOD-500 on various species and ages of ungulates.

CB-6, expandable collar with breakaway
This collar is the same as the CB-5, with the addition of a stitched elastic breakaway tab that separates as tension is applied.