# The difference between killing and eating: ecological shortcomings of puma energetic models

> How much does a puma really need to kill? By following GPS-collared pumas to more than 2000 clusters in Chile, Colorado and California and reading the signs at each kill, researchers found that pumas killed about 10 kg of prey a day, roughly three times what they ate. Energetic models based on body weight and activity predicted what pumas eat fairly well, but badly underestimated what they kill.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2014-elbroch-allen-difference-killing-eating-ecological/

## Citation and access

- **Authors:** L. Mark Elbroch, Maximilian L. Allen, Blake H. Lowrey and Heiko U. Wittmer
- **Year published:** 2014
- **Journal or source:** Ecosphere
- **Full citation:** Elbroch, L. M., Allen, M. L., Lowrey, B. H. and Wittmer, H. U. 2014. The difference between killing and eating: ecological shortcomings of puma energetic models. Ecosphere 5(5): 53.
- **DOI:** 10.1890/ES13-00373.1
- **Access status:** Open access (CC BY 3.0)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2014_Elbroch_and_Allen_etal_the-difference-between-killing-and-eating-ecological-shortcomings-of-puma-energetic-models.pdf

## Tags

- **Species:** Mammals > Mountain lion
- **Region:** South America > Chile; North America > United States
- **Tracking:** Bones; Feeding signs; Hair; Kill sites; Snow tracks; Tracking; Tracks; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Daily travel distance; Energy budget; Feeding; Hunting; Kleptoparasitism; Movement; Predation; Scavenging
- **Methods and technology:** Analysis of variance (ANOVA); Camera traps; CyberTracker; CyberTracker Tracker Certification; Direct observation; Geographic Information System (GIS); Global Positioning System (GPS) collars; GPS cluster analysis; Linear regression
- **Data type:** Modelling or theoretical; New field data
- **Observer qualification:** Certified trackers
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2014

## Detailed keywords

- **Species:** Studied: puma (Puma concolor), 26 individuals (10 males, 16 females) and their kittens. Prey in Patagonia: guanaco (Lama guanicoe), huemul (Hippocamelus bisulcus), domestic sheep (Ovis aries), introduced European hare (Lepus europaeus); the appendix also gives prey weights for Patagonian haired armadillo (Chaetophractus villosus), culpeo fox (Lycalopex culpaeus) and upland goose (Chloephaga picta). Prey in Colorado: elk (Cervus canadensis), mule deer (Odocoileus hemionus), American beaver (Castor canadensis) and North American porcupine (Erethizon dorsatum). Prey in California: black-tailed deer (O. h. columbianus), one American black bear (Ursus americanus), black-tailed jackrabbit (Lepus californicus), northern raccoon (Procyon lotor) and California ground squirrel (Otospermophilus beecheyi). Present but never documented as puma prey: cattle (Bos primigenius) in Colorado; feral pigs (Sus scrofa) and Tule elk (C. e. nannodes) in California. Scavengers at puma kills: Andean condor (Vultur gryphus) and culpeo fox in Patagonia (eleven vertebrate species in all); American black bear, coyote (Canis latrans), golden eagle (Aquila chrysaetos) and common gray fox (Urocyon cinereoargenteus) in Colorado; American black bear, common gray fox, coyote, turkey vulture (Cathartes aura) and common raven (Corvus corax) in California. Comparisons discussed: wolves (Canis lupus) and African wild dogs (Lycaon pictus).
- **Location and habitat:** Three study areas. (1) Patagonia, Chile: southern Aysén District, north of Lago Cochrane, about 1200 km², including Lago Cochrane National Reserve, Estancia Valle Chacabuco and part of Jeinimeni National Reserve; open Patagonian steppe, lenga (Nothofagus pumilio) forest and ñirre (N. antarctica) shrub communities, 200 to 1,500 m. (2) Western Colorado, United States: near De Beque, about 1100 km² of Bureau of Land Management (BLM) land and private land, mainly the High Lonesome Ranch; pinyon-juniper woodland, Gambel oak, sagebrush and saltbush rangeland, mixed conifer and aspen, 1500 to 3000 m. (3) Northern California, United States: about 1024 km² of the Mendocino National Forest and surrounding private land; grassland and mixed chaparral up to Douglas fir stands, 400 to 2450 m.
- **Topics:** kill rates; consumption rates; bioenergetic models (Ackerman et al. 1986 and Laundré 2005); kill rates in kilograms per day versus ungulates per week; handling time at carcasses; meat abandoned at kills; partial prey consumption; kleptoparasitism (food stealing) and scavenger pressure; female breeding status and kittens; predator-prey modelling; harvest quotas and game management; optimal foraging and the marginal value theorem. Inconsistencies in the paper: the text says Colorado pumas were followed over 11 monitoring periods, but Table 1 lists 12 (puma P07 twice), and 12 are needed for the stated total of 45; the text gives monitoring periods of 26 to 368 days, but the longest period in Table 1 is 354 days; the study-site coordinates are labelled “W” and “S” in a way that does not match the locations (for example Colorado “W 39.385, S 108.324”).
- **Statistics or models:** Mixed-model analysis of variance (ANOVA) with individual puma as a random effect, log and root transformations, and Tukey HSD (honestly significant difference) post-hoc tests; multiple linear regression of kill rate on puma weight and mean daily distance; two energetic models (Ackerman et al. 1986; Laundré 2005); GPS cluster definition: 2 locations (Patagonia, Colorado) or 3 locations (California) within 150 m, with at least one at night or at dusk or dawn; ArcGIS 9.1 for distances; a 1.6 correction factor for straight-line distances.
- **Data type:** New field data from GPS-collared pumas (captures in Patagonia March to August 2008 and May to September 2009; in Colorado February 2010 to March 2012; in California December 2009 to November 2012), compared with predictions from published energetic models. Prey weights estimated from the literature (appendix).

## Synopsis

### 1. What they did

Scientists often use energetic models to estimate how much prey a hidden, hard-to-watch carnivore must kill. These models work from the predator’s body weight and how active they are. The authors tested two common assumptions behind such models: that body weight and activity alone are enough to predict kill rates, and that predators eat everything they kill.

They compared puma kill rates measured in the field with the rates predicted by two published puma energetic models (Ackerman et al. 1986 and Laundré 2005). The work covered three very different study areas: Chilean Patagonia, western Colorado and northern California.

- Capturing pumas. Pumas were mostly caught with hounds, which chased them up trees or onto rocks; box traps and foot snares were also used. Each puma was fitted with a Global Positioning System (GPS) collar that took a location every 2 hours.

- Finding kills. The team visited GPS clusters (groups of locations close together) that included at least one location at night or at dusk or dawn. They searched each site for prey remains (hair, skin, rumen and bone fragments). From the state of the remains, bite marks and which body parts were eaten, they decided whether the puma had killed the animal or was scavenging.

- Measuring kill and eating rates. They calculated kill rates in kilograms of prey per day and in ungulates (hoofed animals) per week, for monitoring periods of at least four weeks. They estimated how much each puma ate from the number of days they stayed at a kill, using feeding trials with captive pumas, and added kittens’ share for mothers.

- Testing the models. They ran both energetic models for each puma and each monitoring period, and tested whether puma weight and daily travel distance predicted the field kill rates.

### 2. What they found

The pumas and their kills

- 26 pumas (10 males, 16 females) were followed over 45 intensive monitoring periods of 26 days to about a year.

- Patagonia: 694 GPS clusters checked, 433 kills and 6 scavenging events. Prey included 302 guanacos, 41 domestic sheep, 7 huemul and 83 smaller animals.

- Colorado: 1001 clusters checked, 437 kills and 8 scavenging events. Prey included 266 mule deer, 71 elk and 106 smaller animals.

- California: 396 clusters checked, 215 kills and 4 scavenging events. Prey included 176 black-tailed deer, 1 black bear and 38 smaller animals.

Models versus the field

- Field kill rates averaged 10.10 kg of prey per day. The Ackerman model predicted 4.04 kg per day and the Laundré model 2.44 kg per day. All three were statistically different.

- Estimated consumption (what pumas actually ate) averaged 3.35 kg per day in the field, 2.75 kg per day from the Ackerman model and 1.66 kg per day from the Laundré model. The models came much closer to what pumas ate than to what they killed.

- On average, pumas killed about three times more meat than they ate.

- Neither puma weight nor daily travel distance, the very variables the models use, explained differences in kill rates.

Kill rates across places and pumas

- Kill rates in kilograms per day did not differ between the three study areas or between males and females, even though the areas differed in climate and had one to three ungulate prey species.

- Only females with kittens over 3 months old killed more than females without kittens.

- Kill rates in ungulates per week did differ between areas: higher in California than in Colorado. The authors link this to the big differences in prey size, from deer and sheep of about 40 kg to bull elk of up to 385 kg.

- Handling time at carcasses and the amount of meat abandoned did not differ significantly between areas.

- These kill rates were the highest reported for pumas at the time.

### 3. What they concluded

- Energetic models based only on body size and activity badly underestimate puma kill rates, though they may estimate how much meat a puma needs to eat reasonably well.

- Kill rates in kilograms per day are better for comparing pumas across different places; kill rates in ungulates per week are better for modelling predators and prey within one place.

- Why pumas kill so much more than they eat is still unclear. They may leave carcasses once staying no longer pays, or lose kills to dominant competitors. In Patagonia, scavenging condors had already been shown to raise puma kill rates.

- Rather than refining energetic models further, future research should study the behaviour behind kill rates and the meat pumas abandon.

### 4. How tracking was or was not used

GPS clusters showed where pumas spent time, and tracks and signs at those sites showed what had happened there. Observers searched kill sites for prey remains (hair, skin, rumen and bones) and used the state of the remains, the presence and position of bite marks, and which body parts had been eaten to tell a kill from scavenging. They also recorded the species, age and sex of the prey, ageing ungulates from their teeth. Kittens with mothers were counted partly from tracks in snow, as well as from cameras at kill sites and direct observation. Pumas were captured with hounds, but the paper does not describe people following tracks.

### 5. Tracker or observer certification

Ninety-three percent of all field investigations of GPS clusters were done by CyberTracker-certified observers (citing Evans et al. 2009 and Elbroch et al. 2011). The authors say this ensured a consistent field effort and expertise across the three study areas. The certification level is not given.

### 6. Other technologies, skills or innovations

- GPS collars (Lotek 7000SAW or Lotek Iridium 2D) sending data by Argos or Iridium satellite links.

- ArcGIS mapping software to measure distances, and handheld GPS units to guide observers to clusters.

- Remote cameras at active kill sites.

- Prey weights estimated by age and sex from tooth eruption and wear and from published growth rates (appendix).

### 7. Implications for conservation (from the paper)

- Underestimating predator kill rates could contribute to declines of prey such as bighorn sheep and mule deer.

- For game species, underestimated kill rates may lead to hunting quotas that are set too high.

- Estimates of livestock losses to pumas depend on accurate kill rates.

- Underestimated kill rates would lead to overestimates of how many predators a prey population can support.

- Pumas leave large amounts of meat that feed many scavengers, so models that include this would better show their role in ecological communities.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- The study’s central figures depend on reading tracks and signs at kill sites: whether a puma killed or scavenged, which prey it was, and how old. GPS alone shows only where a puma stopped.

- The authors chose certified observers for most cluster visits so that field effort and skill would be consistent across three study areas in two countries, a practical example of certification supporting comparable data.

## Cite this summary

Lawrence, K. 2026. Summary of: The difference between killing and eating: ecological shortcomings of puma energetic models (Elbroch and Allen et al., 2014). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2014-elbroch-allen-difference-killing-eating-ecological/