Chase reconstructions

The duration, distance, average speed, elevation change, and number of hounds involved in each recapture are summarized for hounds and pumas in Table 2. We present individual chase tracks and parameters (Figs. 1, S2–S4) as well as a Google Earth Pro (earth.google.com) visualization of chase 4 generated from synchronized puma and hound collar data (Video S1). In general, mean chase distance was three times farther for hounds (1,020 ± 249 m) than pumas (335 ± 63 m, t(6) = − 2.66, p = 0.037, Table 2) because we released hounds from a distance great enough to not startle pumas prior to release. In this way, we measured the complete and varied escape maneuvers of the puma in response to the approaching hounds. As a result of these longer pursuit distances, hound chase duration (08:59 ± 03:05 mm:ss) was longer than the associated escape time in pumas (03:48 ± 01:16 mm:ss). Compared to the initial escape, each puma’s second escape was shorter in both distance (247 ± 69 vs. 423 ± 60 m) and duration (01:53 ± 00:56 vs. 05:44 ± 01:12 mm:ss, Table 2).

Figure 1: Chase 1 pursuit (red lines = hounds) and escape (blue line = puma) paths (A), including the elevation profile for Brandy, a GPS-accelerometer collar equipped hound. Insets display ODBA (g, B), speed (ms−1, C), and estimated mass-specific metabolic demand ( V ̇ O 2 in ml O 2 kg−1min−1, D) For (B), (C), and (D), mean values are presented as dashed horizontal lines, and solid horizontal lines in (D) depict V ̇ O 2 MAX for each species. Tortuosity plots (proportion of turns in each compass direction, (E) and the elevation profile for the accelerometer-GPS-equipped hound (F) are also presented. Map data© 2016 Google.

Hound Puma Hounds (n) Distance (m) Duration (mm:ss) Avg. speed (ms−1) Elev. Gain/ Loss (m) Distance (m) Duration (mm:ss) Avg. speed (ms−1) Elev. gain/loss (m) Chase 1 5 1,270 07:37 2.78 228/−161 482 06:56 1.16 121/−84 Chase 2 5 1,400 15:13 1.53 306/−157 178 02:48 1.06 70/−32 Chase 3 4 1,120 12:08 1.54 99/−339 363 04:15 1.33 88/−139 Chase 4 4 291 00:59 4.93 80/−75 316 00:57 5.54 89/−110 Average 1,020 08:39 2.7 178 (54) 334.8 03:44 2.27 92 (11) (250) (03:05) (0.8) −183 (56) (62.8) (01:15) (1.09) −91 (23) DOI: 10.7717/peerj.3701/table-2

As predicted, tortuosity (total distance traveled divided by straight-line distance from start to end point of run) did not differ significantly between hounds and pumas when all individuals and chases were grouped (t (22): 1.04, p = 0.31; Table 3) because the scent hounds roughly followed each puma’s escape path. Overground distance traveled averaged 2.3 to 2.9 times farther than straight-line distance, indicating extent of turning maneuvers while running through rugged terrain. To prolong the time until captured, pumas employed several adaptive strategies that compensated for physiological constraints and being outnumbered. Evasive maneuvers such as temporarily jumping into trees, running hairpin turns or figure-of-8 patterns, and fleeing up steep, wooded hillsides were all used repeatedly to increase escape distance and postpone being overtaken (Table S1). For example, when the hounds were within 35 m of puma 36 M (chase 1), the puma ran a figure-of-8 pattern and briefly jumped into a tree. As a result, hound-puma separation distance increased by nearly 15 m, and the puma’s capture was delayed by an additional 5 min (Fig. S5).

GPS speed (ms−1) Accel. speed (ms−1) Chase Species (animals) Path tortuosity Avg. Max. Avg. Max. 1 Hounds (n = 5) 2.01 ± 0.08 2.33 ± 0.09 8.53 ± 0.29 3.07 ± 0.07 5.2 Puma 36 M 2.22 0.93 ± 0.21 5.27 3.69 ± 0.27 14.5 t = − 6.5 t = 2.3 p < 0.01* p = 0.02* 2 Hounds (n = 5) 3.61 ± 0.21 1.53 ± 0.03 7.5 ± 0.45 2.43 ± 0.05 5.93 Puma 36 M 3.34 0.56 ± 0.17 2.89 3.49 ± 0.34 15.0 t = − 6.4 t = 3.1 p < 0.01* p < 0.01* 3 Hounds (n = 4) 1.98 ± 0.09 1.35 ± 0.04 5.5 ± 0.87 3.32 ± 0.06 6.4 Puma 26 M 4.95 0.48 ± 0.11 2.38 2.85 ± 0.2 11.8 t = − 8.7 t = − 2.2 p < 0.01* p = 0.03* 4 Hounds (n = 4) 1.42 ± 0.06 3.04 ± 0.2 5.89 ± 0.45 5.35 ± 0.15 6.35 Puma 26 M 1.15 2.32 ± 0.51 3.86 11.06 ± 0.5 14.49 t = − 1.4 t = 12.1 p = 0.16 p < 0.01* Avg. Hound 2.32 ± 0.24 1.7 ± 0.03 7.0 ± 0.38 3.89 ± 0.18 5.97 ± 0.28 Puma 2.92 ± 0.52 0.74 ± 0.09 3.6 ± 0.63 2.94 ± 0.04 13.9 ± 0.73 t = 1.04 t = − 10.4 t = − 3.9 t = 5.2 t = 10.3 p = 0.31 p < 0.01* p < 0.01* p < 0.01* p < 0.01* DOI: 10.7717/peerj.3701/table-3

Overall average chase speed, as measured by chase distance divided by chase duration, was similar between species (2.7 ± 0.8 m s−1 and 2.3 ± 1.09ms−1 for hounds and pumas, respectively; t(6) = − 0.31, p = 0.77, Table 2). However, GPS-derived average speeds from all hounds (including those not outfitted with accelerometers) and pumas suggested that, across chases, hound pursuit speed was twice that of the escaping pumas (1.7 vs. 0.74ms−1 for hounds and pumas, respectively; t(1870) = − 10.4, p < 0.01; Table 3, Fig. 2), since pumas spent larger proportions of each encounter stationary (avg. 31% vs. 15% stationary for pumas and hounds, respectively; t(6) = 1.37, p = 0.22). Using accelerometer-derived speed estimates (Eqs. (3) and (4)) to resolve running dynamics in finer temporal resolution, we note that pumas briefly hit peak speeds in excess of 14ms−1, more than twice the top speed of the pursuing hounds (5.2–6.3ms−1, Table 3). Puma escapes were characterized by sequential high-speed evasive maneuvers interspersed with slow, low acceleration periods (Fig. 3). In contrast, hound pursuit speeds were more constant over the course of each chase (Fig. 1C and Figs. S2–S4C).

Figure 2: GPS-derived pursuit and escape speeds for hounds (red) and pumas (blue), respectively, during all chases. The mean (±SE) speeds, in m/s, for hounds (1.7 ± 0.03) and pumas (0.74 ± 0.09) are depicted as dashed vertical lines.

Figure 3: Escape acceleration signatures of adult male pumas 36 (A, B) and 26 (C, D). Acceleration (g) is scaled to the same range for comparison. Chase distance is in m and chase duration is in mm:ss. Colors correspond to pumas’ accelerometer-GPS collar orientation in the X (transverse sway, black), Y (anterior-posterior surge, blue), and Z (dorsal-ventral heave, red) planes.

Immediately after release, all hounds concurrently worked to detect the nearby puma’s scent and give chase. Average hound chase speed did not differ across individuals for both pursuits of puma 36 M (chase 1: 2.52 ± 0.07ms−1, F 4,711 : 0.71, p = 0.59; chase 2: 1.74 ± 0.03 m s−1, F 4, 1,653 : 1.95, p = 0.1), but Hound 4 (Crocket) was significantly slower than the three other hounds during both pursuits of puma 26 M (Hound 4: 1.37 ± 0.06ms−1, others: 1.71 ± 0.04ms−1; t 988 : −4.4, p < 0.001). This was probably a result of Hound 4’s age (11), over twice as old as the other hounds (average age of 5) involved in 26 M’s recapture. Hound group cohesion (the spacing of individual members in proximity to the moving group centroid, measured every 3 s) varied across chases (Fig. 4), likely due to interacting effects including pack composition, individual characteristics (e.g., experience, age, sex), topographic complexity, and puma scent freshness. Tighter spatial clustering was observed between the five members of the hound pack pursuing puma 36 M (Figs. 4A and 4B) than that of the 4-member pack that chased puma 26 M (Figs. 4C and 4D). Across chases, the maximum path deviation of individual hounds from the centroid of the moving group averaged 13.1 (±2.8) meters. No single hound was ever beyond 55 m of the true path of the puma, although the average maximum deviation was 19.1 ±11.7 m.