Pugmarks and the biology of the Bobcat, Lynx rufus

1. What they did

Most of what was known about bobcat social life came from hunters, naturalists, pet owners, radio-tracking and captive animals. The author lived inside the home range of a female bobcat who was habituated to her and had raised a litter every year since 1976. In 1980 she found that on the sandy soils of central Florida she could follow individual bobcats by their pugmarks (footprints).

From May 1980 to August 1981 she followed this female, her two cubs (one male, one female) and her adult male consort at Archbold Biological Station, Florida:

• Telling individuals apart. When she saw a bobcat, she traced its pugmarks onto a transparency laid on a pane of glass in a levelled wooden frame. She also recorded soil moisture and made tracings under different soil conditions. Bobcats were also identified by size, facial markings and colour patterns.
• Following them. She tracked mostly in the morning, while the sand was moist with dew, along firelanes and trails the bobcats used. She walked over 1,600 km, mapped the data daily, and saw the bobcats 138 times, from fleeting glimpses to hours at a midday resting place.
• Recording behaviour. Observations were tape recorded and transcribed daily.

2. What they found

Identifying individuals

• She could easily identify the pugmarks of 3 adults and 2 cubs. The female’s differed from the two adult males’ in size and pad position. The cubs’ pugmarks were smaller, and the male cub’s were broader than the female cub’s. The consort male had two splayed toes on his left forepaw.
• She traced walking tracks only, because when a bobcat runs the hind feet tend to land in the front-foot prints.

Raising the cubs

• The cubs were born in the first week of May 1980 in a dense bayhead. On 28 June the mother moved them 1.2 km east, then on to a stand of rosemary. Through the summer they stayed in the centre of the range, using each resting place for 2 to 6 days, always near rosemary or palmetto for shelter.
• The cubs nursed until the end of their fourth month. The author first saw them given food (a cotton rat) at about 11 weeks. As they grew, they had to chase their mother for food. Uneaten food was sometimes covered with vegetation and picked up again before leaving.
• Calls: the cubs gave high-pitched distress calls when alarmed; the mother answered with a reassuring “yeow-yeow”, and used an “arf-arf”, like a small barking dog, to keep them from following.

Scent and scrapes

• Smell was an important way of communicating. The mother sprayed a mist from the anal region when leaving a resting place, and cubs greeted her by raising their tails onto her and spraying. Licking and grooming were common.
• Scrapes were rare on firelanes in summer. From late August the mother scraped about every 100 m in the centre of the range, and from 23 November until February scrapes were as common as every 50 m along trails. Liquid, probably urine with anal sac secretions, was placed in them.

Dispersal and home range

• The cubs began to leave scent in scrapes in December, at 8 months. The family last moved together on 15 January 1981. The male cub stayed in the south of the range and the female cub settled in the northeast; they were not seen together again.
• The mother’s home range from birth to dispersal was 6.45 km². In January she left about 1.77 km² of it to her cubs. The male cub used 0.65 km² of it plus 1.04 km² to the south; the female cub used 1.12 km² plus 0.22 km² to the northeast.
• By mid-June 1981, with a new litter, the mother again used her whole range. The 1980 cubs, then about 14 months old, and their pugmarks were no longer found.

The consort and breeding

• The female and the adult male shared the range. They were first seen meeting on 8 September 1980, and the male was near the family four more times, for up to five hours.
• From late January to March 1981 their tracks often met and crossed. In the last two weeks of January the female travelled to each end of her range at least daily. She was believed to be in estrus from 29 January to 6 February (9 days): signs were small, wet, brown scats, spraying on vegetation and a tolerant, calm manner. An adult male from the northeast was tracked in her range during this time, and she was later seen with a wound on her nape.
• She gave birth to her sixth litter on 4 or 5 April 1981, 57 ± 1 days after the last day of estrous behaviour. The consort rested with her for several hours on 20 to 22 April and 8 to 9 May, about 2.12 km from her den.

3. What they concluded

• Cubs stayed near their birthplace for about 2 months; after 3 months the mother moved them around the home range, giving them knowledge of it and hunting experience.
• Bobcats left their natal area after a period of solitude in a familiar part of it. The cubs did not leave until their mother’s next litter left the natal den, so the home range stayed occupied.
• Her observations suggest a relatively monogamous pair that may share in keeping the home range boundaries. The male travelled more widely than the female while she cared for cubs. The pair’s meetings during pregnancy and after birth may help keep their bond.
• Males from neighbouring ranges are probably drawn by the scent the female sprays along the boundaries in the breeding season, which may explain the overlap between male home ranges reported elsewhere.
• Pugmarks are a valuable way to identify and study bobcats on the sandy soils of Florida. They avoid trapping, which can take hundreds of trap nights and may miss transient or trap-shy animals and much behaviour. Identifying individuals by their pugmarks could give a better index of bobcat numbers at scent stations, and the larger pugmarks of male cubs could provisionally show the sexes in a litter.
• The technique needs further careful testing before it is used to monitor larger populations.

4. How tracking was or was not used

Tracking was the main method. The author identified individual bobcats from traced pugmarks and followed their tracks daily on sandy firelanes, trails and roads to map movements, home ranges and dispersal, and to find dens and resting places. Tracks showed where the female and the males met, crossed and parted (for example, she trailed the male 1.34 km west and the female over 1.50 km north on 19 February 1981). She also read scrapes, sprayed vegetation and scats, using moist scats as one sign of estrus. She notes that cat hunters in California have long identified and followed tracks, and that snow tracking has been used to measure bobcat home ranges in the north.

5. Tracker or observer certification

Not reported. The author did all the tracking herself; her tracking experience is not described or tested. The findings rest on her identification of individual pugmarks.

6. Other technologies, skills or innovations

• A simple pugmark tracer: a 15 × 23 cm pane of glass in a wooden frame, levelled over the track with flat-headed bolts at each corner, with a transparency traced using a fine felt-tip pen. Chester Winegarner made the tracer.
• Distances calculated on a computer graphics tablet; observations tape recorded.

7. Implications for conservation (from the paper)

• Bobcats are hunted in Florida and other states and their habitat continues to be destroyed, so knowing how adults move and how young disperse is needed for proper management.
• Monitoring by pugmarks avoids trapping and can include trap-shy and transient animals that trapping misses.