Counting Pumas by Categorizing Physical Evidence

1. What they did

Pumas are secretive, but they leave plenty of tracks and urine markers (scrapes). The hard part is knowing how many pumas made them: the most common mistake is counting one animal’s many tracks as several pumas. The authors, professional puma hunters and field biologists who have captured pumas for telemetry studies in North and South America since the early 1960s, set out a way to count individual pumas from physical evidence alone. They used it to produce an annual count of Florida panthers from 1981 to 2007.

They divided the panther range in southern Florida into nine survey units. Team members searched trails, firebreaks, old swamp buggy tracks and logging and ranch roads from all-terrain vehicles (ATVs) and swamp buggies, year round. Tracks of radio-collared panthers could be told apart using telemetry, so the work focused on un-collared animals. To separate individuals they used three rules:

• Gender. From track size (heel pad width) or stride length measured in a slow walk on level ground. Adult female strides were 46 to 55.5 cm and adult male strides 61 to 74 cm. Track size was never used to identify individuals.
• Time. Only tracks known to be less than 24 hours old were compared. Rather than judging how weathered a track looked, they used known events: a rain or wind the day before, tracks on top of their own vehicle tracks, roads brushed with a drag the previous day, or scent still fresh enough for trained hounds.
• Distance. Fresh tracks of the same sex found within the same 24 hours were counted as different animals only if they were more than 10 km apart (females) or more than 17 km apart (males). These distances came from their own experience trailing pumas with hounds, and were checked against movement data from collared panthers.

Occasionally a track had a unique feature (crooked or missing toes, a crooked foot, an injured heel pad) or a female had juveniles with her, which allowed an individual to be identified. To check the counts, they compared them with captures, trail cameras, and three other measures: captures per day of hunting with hounds, highway deaths, and males dispersing north of the Caloosahatchee River.

2. What they found

The annual count

• From 1981 to 1994 the count ranged between 19 and 30 adult and juvenile panthers. The low point was in 1991, after 7 juveniles and 3 newborn kittens were removed for a captive breeding programme.
• After 8 female pumas from Texas were released in 1995 to counter inbreeding, the count rose to 117 by 2007.

Support for the distance rules

• In unpublished daily location data (1995 to 1998), 99% of 3015 female 24-hour movements were under 9.6 km, and 99% of 824 male movements were under 16.7 km.
• Two panthers with hourly GPS collars moved at most 7.4 km (female) and 8.2 km (male) from their starting point in 24 hours.

Checking the count

• In Everglades National Park in 1985 and 1986, tracks showed one adult male (whose sign disappeared in October 1986) and seven others: one adult female without young and two females with two juveniles each. The two families were separated by fresh tracks more than 10 km apart on the same day. Capture work from November 1986 treed all seven, and no further un-collared panthers were found.
• In spring 2000, track counts in the same unit showed one un-collared female besides six collared panthers. A trail camera survey also recorded only one un-collared female, who was then treed and collared. An un-collared male who arrived the next fall was detected by tracks, then confirmed on camera.
• Over 27 years, the authors had no example where survey and capture results differed by more than one or two panthers.

The other indices

• Highway deaths averaged 1.4 per year from 1981 to 1997, 3 per year in 1998 and 1999, and 10.8 per year from 2000 to 2007, with a record 15 in 2007, despite fencing and underpasses that ended deaths where they were built.
• Before 1995 each capture took an average of 18.7 days of hunting effort; from 1995 to 2007 it took 5.5 days, a 3.4-fold rise in capture rate, even though capture seasons were shorter and more targeted.
• Ten males were recorded north of the Caloosahatchee River from 1981 to 1991, none from 1992 to 1997, and 17 from 1998 to 2007. No females or signs of breeding have been found there.
• All indices showed similar patterns to the annual count.

Limitations they noted

• Same-sex adults close together cannot be separated by the distance rule, but repeated searches give chances to find their tracks far enough apart.
• Track size varied widely along a single panther’s trail as the animal stepped from wet to dry sand or from mud to firm ground.
• After 1990 they lost access to most private land (22% of the occupied range), so some panthers there may have gone undetected.
• Dispersing young males may be counted in more than one unit; the authors judged this within acceptable limits.

3. What they concluded

• Pumas may be secretive, but they can be counted. Qualified trackers can use gender, time and distance to run synoptic surveys, both to set hunting quotas and to measure the recovery of endangered populations.
• The method relies entirely on verifiable physical evidence and avoids the need to identify individuals by track size.
• It is effort dependent: it needs either many qualified observers over a short time or one qualified observer returning to the same areas over a longer time.
• An experienced puma hunter, searching where pumas concentrate their movements and helped by trained hounds, can survey large areas with more dependable results than searches set up with transects or grids.
• The method could be used to count isolated populations of other large cats, especially in snow or conditions like those in southern Florida. The authors encourage testing it in other places.

4. How tracking was or was not used

Tracking was the core of the study. Trackers searched for, identified and recorded panther tracks and urine markers, sexed animals from heel pad width and stride, aged tracks by known events, and used distances between fresh track sets to count individuals. Unusual track features sometimes identified individuals. Trained hounds trailed panthers by scent and treed them in areas where tracks could not be seen, and the authors based their distance rules on their experience trailing pumas with hounds. Tracks of panthers were also photographed and their positions recorded on data sheets.

5. Tracker or observer certification

Other experienced trackers. No certification is reported. The trackers are described as “qualified trackers”, meaning professional puma hunters or wildlife biologists who have been extensively trained to locate and identify puma sign. The authors themselves have hunted and captured pumas since the early 1960s. Their track-based counts were checked against captures and trail cameras in Everglades National Park, where all predicted animals were treed and no others were found.

6. Other technologies, skills or innovations

• Trained hounds, descended from the original pack, used consistently for 27 years for trailing and capture.
• Radio telemetry of 157 collared panthers, used to tell collared animals’ tracks from un-collared ones.
• Handheld Global Positioning System (GPS) units for recording locations, and hourly GPS collars for movement data.
• Data sheets and photographs as documentation of the physical evidence.
• Trail cameras as an independent check on the count.

7. Implications for conservation (from the paper)

• Under the Endangered Species Act, recovery decisions should rest on the best available science, and the authors argue this science should rely on verifiable physical evidence. The annual count has been used since 1981 for major panther management decisions, such as captive breeding and genetic restoration.
• Sightings, interviews and questionnaires gave unreliable estimates, from extinct to 300 panthers.
• Care is needed when comparing the annual count with the number of breeding adults in a minimum viable population, because some panthers do not breed.
• The count will remain important as the isolated population faces habitat loss, inbreeding and the unknown effects of Everglades restoration.