# Investigating the feasibility of a passive tracking index for monitoring wildlife in the Lower Omo Valley, Ethiopia

> Can a few strips of raked soil across a dirt road help manage wildlife where money and equipment are scarce? In Ethiopia’s Lower Omo Valley, a local tracker read the tracks on twenty plots for three days, giving activity indices for lesser kudu, dikdik, hyaenas, baboons and guineafowl, and turning up caracal and serval too. The authors suggest the method could guide sport hunting, conflict with people and recovery after anthrax outbreaks.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2007-engeman-evangilista-investigating-feasibility-passive-tracking/

## Citation and access

- **Authors:** Richard M. Engeman and Paul Evangilista
- **Year published:** 2007
- **Journal or source:** African Journal of Ecology
- **Full citation:** Engeman, R. M. and Evangilista, P. 2007. Investigating the feasibility of a passive tracking index for monitoring wildlife in the Lower Omo Valley, Ethiopia. African Journal of Ecology 45(2): 184–188.
- **DOI:** 10.1111/j.1365-2028.2006.00695.x
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2007_Engeman_and_Evangilista_investigating-the-feasibility-of-a-passive-tracking-index-for-monitoring-wildlife.pdf

## Tags

- **Species:** Mammals > Caracal; Mammals > Common genet; Mammals > Guenther’s dik-dik; Mammals > Hyena; Mammals > Lesser kudu; Mammals > Olive baboon; Mammals > Serval; Birds > Vulturine guineafowl
- **Region:** Africa > Ethiopia
- **Tracking:** Track counts; Tracking; Tracks; Tracks and signs identification
- **Methods and technology:** Population trends; Road transects
- **Data type:** New field data
- **Observer qualification:** Reported but not validated
- **Discipline:** Human–wildlife conflict; Population trends; Wildlife tracking
- **Year published:** 2007

## Detailed keywords

- **Species:** Indexed: lesser kudu (Tragelaphus imberbis), Guenther’s dikdik (Madoqua guentheri), hyaena (given as “Hyaena hyaena or Crocuta crocuta”; the paper does not say which species), baboon (Papio anubis) and guineafowl (Acryllium vulturinum). Recorded once each: genet (Genetta felina), caracal (Caracal caracal) and serval (Leptailurus serval). Mentioned: livestock (calves, sheep and goats) taken by hyaenas; sorghum and maize crops raided by baboons. Internal inconsistency: the abstract says baboons were indexed, and the text gives indices for “these four species”, but Table 1 lists five species and gives no two-day index for baboons (“NA”).
- **Location and habitat:** Lower Omo Valley, south-west Ethiopia (05°30′N, 36°00′E to 05°00′N, 36°3′E), about 75 km north of the Ethiopia and Kenya border. Savanna bushland on the east side of the Omo River, along a low-use dirt road with fine-grained soil. A buffer zone between the territories of the Hamar, Bume, Galeb and Karo peoples, which tribal conflict has left lightly grazed and disturbed; a sport hunting concession.
- **Topics:** passive tracking index (PTI); track plots; population monitoring with few resources; sport hunting and sustainable harvest; human–wildlife conflict (livestock predation, crop raiding); wildlife disease (anthrax); detecting cryptic species such as cats; effect of rain on track plots; baseline index values.
- **Statistics or models:** Passive tracking index calculated as the mean of daily mean track intrusions per plot (Engeman 2005), with variance from a mixed linear model; variance components (between plots, between days, random) estimated by restricted maximum likelihood with SAS PROC VARCOMP. Index values, variances and standard errors given for three days and for two days.
- **Data type:** New field data: twenty track plots checked on three consecutive days. The paper does not give the dates of data collection.

## Synopsis

### 1. What they did

Wildlife managers in much of Africa have little money, equipment or trained staff, so they need monitoring methods that are simple and cheap but still show real changes in animal numbers. The Lower Omo Valley in south-west Ethiopia holds a great variety of wildlife. Conflict between local peoples has left a buffer zone where few cattle graze, the area is known for sport hunting, and anthrax outbreaks periodically kill large numbers of animals.

The authors tested whether a passive tracking index (PTI), already used to monitor carnivores, marsupials and hoofed animals in North America and Australia, could work there:

- Track plots. Twenty plots were placed at random along a little-used dirt road, at least 0.5 km apart. Each plot was raked and smoothed into a strip 1.5 m long across the road (about 3 m wide). The fine soil held tracks very well.

- Counting. Every 24 hours the plots were checked, the number of sets of tracks crossing each plot was counted for each species, and the plots were smoothed again. This ran for three consecutive days.

- Identification. A tracker from the local hunting concession identified the tracks.

- The index. For each species, the index is the average over days of the average number of track sets per plot, with a measure of its variability.

### 2. What they found

- A rainstorm on the first day may have wiped out some tracks, so that day may represent less than 24 hours of tracks. The authors calculated index values both with all three days and with only the two rain-free days.

- Index values were calculated for lesser kudu, Guenther’s dikdik, hyaena, baboon and guineafowl.

- Using the two rain-free days, the indices were: dikdik 0.350, guineafowl 0.275, hyaena 0.225 and lesser kudu 0.075. These were up to 50% larger than the values that included the rain day. Baboons had an index only for all three days (0.083).

- A genet, a caracal and a serval each crossed a plot once.

- There was no sign in the tracks that any species avoided or was drawn to the plots.

### 3. What they concluded

- The index worked for two hoofed species, a carnivore and a ground-feeding bird, which would already be useful for general management.

- Some species would need surveys timed to their migrations or placed in the pockets of habitat they use.

- These values could serve as a baseline for future monitoring, but permanent plot locations should be set up for following trends.

- Index values should not be compared between species, because two species with the same numbers can be active to different degrees. Trends over the same period can be compared.

- The method needs no expensive or high-tech equipment and no great technical expertise, and is unlikely to change how animals move. It suits sustainable sport hunting, human–wildlife conflict and tracking the impact of, and recovery from, disease.

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

The whole method rests on tracks. Prepared strips of soil across a road were checked each day, and a tracker from the hunting concession identified the species from the tracks and counted how many sets of tracks crossed each plot. The tracks also showed that animals did not seem to avoid or be attracted to the plots. No trailing was reported.

### 5. Tracker or observer certification

Not reported. The tracks were identified by “a tracker from the local hunting concession”. Nothing is said about the tracker’s experience or any test of their skill, although every index value depends on their identifications, and the hyaena tracks were not assigned to either of the two species named.

### 6. Other technologies, skills or innovations

- Raked and smoothed track plots on a dirt road, re-smoothed each day.

- A statistical approach (Engeman 2005) that gives an index and its variance without assuming that plots or days are independent, using SAS software.

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

- Lesser kudu and the other indexed mammals are hunted for sport, bringing licence fees (for example US$1500 for a lesser kudu) and concession income to the region. A simple index could support sustainable harvests and a stable income.

- Hyaenas take calves, sheep and goats from pastoralist families and occasionally attack people; baboons raid sorghum and maize, especially for the Karo. Monitoring can inform how these conflicts are managed.

- Anthrax killed wildlife and livestock in 2000 and 2001, and over 2000 lesser kudu carcasses were burned. Hyaenas and baboons were thought to be hard hit, but they tend to die in dens and thick cover. An index could show losses and recovery in species whose carcasses are rarely found.

- African cats are hard to monitor. Finding caracal and serval tracks suggests a larger survey might index them too.

- Changes in the intensity of conflict between local peoples would also show in the indexed species.

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

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

- The study shows how much a single day of rain can change a track count: index values went up by as much as half once the rain day was left out. Weather on survey days is worth recording.

- The index is only as good as the identifications. Where two similar species share an area, such as the two hyaena species named here, a tracker able to tell their tracks apart would make the counts more useful.

## Cite this summary

Lawrence, K. 2026. Summary of: Investigating the feasibility of a passive tracking index for monitoring wildlife in the Lower Omo Valley, Ethiopia (Engeman and Evangilista, 2007). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2007-engeman-evangilista-investigating-feasibility-passive-tracking/