This is the question NBCS gets asked most frequently and is, frustratingly, the most difficult to answer.
To estimate the number of coyotes properly about 100 coyotes would need to be captured, marked, released and recaptured. Most coyotes are way too tricky to step into a trap twice. Because coyotes are so clever, this type of estimate is rarely if ever used for coyotes: it is labor intensive, cost prohibitive, and estimates are inaccurate.
NBCS instead works on determining the number of packs (family groups) and uses this as a index to population size. Based on our research we estimate there are between 10 and 14 resident packs on Aquidneck Island and 3-5 resident packs on Conanicut Island (Jamestown). Each pack will normally have 3-7 adults and 2-7 puppies. Community residents have reported up to 21 individuals in some packs and regularly report 7 puppies per pack in urban and suburban areas. The reason for the high numbers is that coyote numbers numbers fluctuate with food availability. In areas where they are receiving food resources number of packs, puppies, and individuals in each pack increase. If food sources are removed numbers of packs, pups, and individuals should all decrease. NBCS plans to initiate and monitor this effort.
We use GPS collars that transmit hourly point locations to estimate the territory size of each pack. We also use observation and motion activated camara traps to get as much information as we can about group size. Observations from islands residents have been very useful as well. People frequently get counts of puppies from April through June and report groups of adults as they observe them on the Coyote Info Line (401) 300- 4695.
Additional Resources: To know how many animals in a population scientists standardly use the Mark and Recapture Method. You capture, mark, and release a number of individuals back into the population. You then trap again and get catch number of coyotes - in theory some are recaptures recognized by the marks. The proportion of individuals marked individuals in the recapture group over the total number recaptured (marked and unmarked) is thought to be proportional to the total number of marked individuals in the population over the number you want to know: the total number of individuals in the population. This works very well for animals that are easy to capture.