Telemetry/ Radio Transmitters

Telemetry studies have been conducted for many years on animals such as large mammals, small mammals, and birds.  More recently, technological advances (e.g., battery miniaturization) have led to smaller radios applied to small animals like snails.

 
What they are:

• Miniature radio-transmitters (weight 1.6 g) used on apple snails are about the size of a dime (see picture below) (Darby et al. 2002).

  

• Each transmitter has a unique radio frequency.

• Transmitter battery life is approximately 60 days.  Longer monitoring would require a staggered entry design (see Darby et al. 2002).

• Aquaria observations show no apparent effect on snail movement.

What the method is used for:

• Radio transmitters are ideal when individual snails must be monitored or located repeatedly.

• Radio transmitters have been used to monitor apple snail movements (e.g., those occurring during changes in water levels) and survival (e.g., during dry down events).

How they are used:

• Transmitters are attached to adult-sized apple snails (>30 mm) using a marine epoxy (aluminum-repair type epoxy [see Darby et al. 2002]).  The area of application should be dried and sanded lightly to ensure proper adhesion.

• A transmitter is placed on the outer shell, 1-2 cm up from the aperture, on the right side of the body whorl, adjacent to the suture (see picture under "What they are").

• Transmitter signals can be detected 100-200 meters from submerged snails.

• Standard telemetry equipment is used to locate the immediate vicinity of transmittered snails.

         

• Precise locations are determined, using magnet induced signal alteration, using a magnetic probe, or “magnet rake” described in Darby 1999 (see picture above right).

Their limitations:

• Radio transmitters are relatively expensive (approximately $150 each).

• The battery life is short (approximately 60-90 days).

• The radio receiver is expensive (approximately $700 [depending on the model]).

Literature Cited:

• Darby, P.  1999.  Radio transmitter retrieval in wetlands using a magnetic probe.  Journal of Field Ornithology 70(4): 587-590.

• Darby, P.C., R.E. Bennetts, S.J. Miller, and H. Franklin Percival.  2002.  Movements of Florida apple snails in relation to water levels and drying events.  Wetlands 22(3): 489-498.

Related Publications:

• Darby, P.C., P.L. Valentine-Darby, and H. Franklin Percival.  2003.  Dry season survival in a Florida apple snail (Pomacea paludosa SAY) population.  Malacologia 45(1): 179-184.

• Darby, P.C., P.L. Valentine-Darby, H. Franklin Percival, and W.M. Kitchens.  2004.  Florida apple snail (Pomacea paludosa SAY) responses to lake habitat restoration activity.  Arch. Hydrobiol. 161(4): 561-575.