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Comparison of the flocking behavior of Katahdin and Rambouillet sheep breeds in an extensive range environment using GPS technology

Animal Biotelemetry volume 13, Article number: 7 (2025) Cite this article

Abstract

Background

There is considerable interest in the suitability of the farm-flock Katahdin hair sheep breed for large-scale extensive range sheep production systems. Flocking behavior or “flockability”, a measure of gregariousness, is critical for sheep to produce in extensive, herded management systems. An evaluation of the Katahdin breed in a Western U.S. range environment compared to the traditional range-adapted Rambouillet breed is underway. The objective was to compare the flockability of range-reared Katahdin ewes to Rambouillet ewes during the summer grazing season using GPS collars. Flockability was measured by how far a ewe was dispersed from the centroid of the study flock and the total daily distance traveled compared to the study flock.

Results

Complete GPS coordinates were available from 23 Rambouillet and 29 Katahdin ewes in 2023 and five Rambouillet and five Katahdin ewes in 2024. Study groups were managed in bands of 800–1,000 ewes with lambs. During the day, the Katahdin breed had a farther dispersion from the study flock centroid for one of the study groups (P < 0.05), the Rambouillet breed was more dispersed for one study group (P < 0.05), and the breeds did not differ for one study group (P > 0.05). The effect size, measured using Cohen’s d, was small for all groups. The daily distance traveled was farther for the Rambouillet breed in two study groups (P < 0.05) when compared to the Katahdin breed, but did not differ for the other study group (P > 0.05). The effect size was low regardless of significance. When individual ewes were compared, both breeds had ewes that were either closer or farther away from the flock centroid (P < 0.05) or ewes that traveled farther or shorter daily distance (P < 0.05).

Conclusions

The Katahdin breed was similar in flockability to the traditional, range-adapted Rambouillet breed, indicating that the Katahdin breed is well suited for grazing in an extensive range environment. This study indicates the Katahdin breed exhibits favorable behavioral characteristics to flock well in large-scale extensive range systems and provides an opportunity for Western U.S. producers interested in incorporating this breed into their flock.

Background

Livestock grazing on extensive, open (non-fenced) rangelands in the Western U.S. has been part of the landscape since westward expansion in the mid-1800’s and is the primary land use in areas not suited for farming [1]. Research at the U.S. Sheep Experiment Station (USSES) has included testing and developing range-adapted sheep breeds in eastern Idaho and southwest Montana for over 100 years [2, 3]. Much different from pasture-based systems in other parts of the U.S., large-scale Western U.S. sheep systems operate on extensive rangelands of rugged terrain inaccessible by vehicles. To cope with predators, limited water resources, sparse forage, and lack of physical fences, sheep are under continuous (24/7) herded (i.e., shepherds) management, where herders dictate daily where sheep graze, water, and bed. Throughout the annual grazing season, sheep may be herded well over 200 km. Accordingly, sheep have been selected to perform and respond to this system.

The Rambouillet is a foundational breed at the USSES and is typical of the “Western white-face” sheep raised throughout the U.S. West. It is well adapted to rugged range conditions and is a dual-purpose breed, producing both lambs and a high-quality fleece. The breed was the foundation of other range-adapted maternal breeds developed at the USSES, including the Targhee [4] and the Polypay [5]. For the purposes of this study, the flocking instinct and behavior of the Rambouillet breed is considered to be the standard representation for range-type ewes grazing extensive rangelands under herded management.

The Katahdin is a hair breed that was developed in Maine in the 1950s from crosses of St. Croix hair sheep with British wool breeds, including the Wiltshire Horn and Suffolk [6]. The Katahdin has become the most registered breed in the U.S. [7]. With the decline of available shearers in the U.S. and the decline in wool revenue (6 to 13%) relative to lamb revenue (76 to 83%), interest in hair sheep that do not need to be shorn has increased [8, 9]. The Katahdin has also exhibited parasite resistance to gastrointestinal nematodes [10,11,12,13,14]. Although primarily raised in small- to medium-sized flocks in the Eastern and Midwest U.S., interest has grown in utilizing the Katahdin breed in open extensive range environments under continuous management of traditional herders. To our knowledge, no research exists describing the flockability of the Katahdin breed under such conditions.

Sheep tend to maintain close spatial and social associations which are paramount for flocking behavior [15]. Flocking, or the aggregation into a large cohesive group, is an evolutionary behavior thought to be due to predation [16]. The suitability of any ewe for herded, open-range grazing depends on her ability to remain with the flock, survive, and wean her lamb(s). The objective of this research was to compare and contrast the flockability of Katahdin ewes with that of traditional, range-type Rambouillet ewes in an extensive, open-range, herded system. Accordingly, GPS collars were deployed on range-reared Katahdin and Rambouillet ewes during the 2023 and 2024 spring and summer grazing seasons at USSES. Flockability, the ability to remain with the flock, was estimated by how far the ewe was dispersed from the centroid of the flock at any given time and the total daily distance traveled throughout the grazing season.

Methods

GPS collars

In 2023, GPS collars (CloudPosition EF3 Sensor) [17] were deployed to 33 Katahdin and 33 Rambouillet ewes at turnout to grazing on May 10. Study ewes were managed as a component of a large sheep bands (800–1,000 ewes with lambs). Study ewes were assigned based on lambing date to one of two bands. Each band was continuously managed by a single herder with working animals (herding dogs, guardian dogs, and horses). Initially, Bands 1 and 2 were subdivided into sub-bands (approximately 250 ewes) in the early spring grazing period (May 10–June 2) but merged into complete bands on June 3. GPS collars were removed on July 10. In 2024, GPS collars were deployed to 27 Katahdin and 32 Rambouillet ewes on May 6. All study ewes were placed in the same band. The early spring sub-bands were combined into complete bands on June 16. GPS collars were removed on July 8. For both years, GPS collars were programmed to record the position every five minutes. Data were retrieved after GPS collar removal.

Animals

Forty Katahdin ewes and two rams were shipped each year from the U.S. Department of Agriculture, Agricultural Research Service, Meat Animal Research Center (USMARC) in Clay Center, NE to the USSES in 2020, 2021, and 2022. Because the Katahdin ewes received from USMARC were reared in fenced, un-herded, pastures systems and not adapted extensive range-based systems, lambs from those ewes were grafted onto range-adapted maternal ewes (Polypay, Rambouillet, or Targhee) within a few hours of birth. Those lambs remained with their foster dam throughout the grazing season until weaning, learning from their foster ewes how to graze and survive in a rugged, extensive environments and respond to herders (including herding dogs, guardian dogs, and horses) under herded management. Fostering of lambs from USMARC-born ewes continued in subsequent years. The Katahdin ewe lambs born, reared under foster range ewes, and retained as replacements at USSES were permanently managed with the range-ewe flock and were allowed to keep their lambs in subsequent years.

In 2023, all available 1- and 2-year-old Katahdin ewes were selected for inclusion in the study (n = 33). Since a larger number of 1- and 2-year-old Rambouillet ewes were available for inclusion in the study, they were chosen based on optimal contribution selection [18, 19] using optiSel in R [20] to identify ewes that were lowly related to each other (n = 33). In 2023, study ewes were 1- and 2-year-olds. In 2024, study ewes were 2- and 3-year olds. All ewes had either one or two lambs and were considered to be lactating throughout the study period. Both breeds primarily produce twins (60% of litters) with remaining litters split between singles and triplets. On average, Katahdin ewes weigh less than Rambouillet ewes (60 kg vs 80 kg). All ewes and lambs were determined to be in good health. There were four Katahdin and four Rambouillet ewes with complete GPS collar data included in both years.

Grazing includes contiguous properties of both private and public lands of a sagebrush-grass community [21]. Elevation ranges from 1,690 to 1,890 m. Over a 10-year period, the mean June and July temperature for the area was 14.4 and 18.8 C, respectively [22]. For the study period, the mean temperatures were 12.6, 18.9, 15.3, and 19.1 C for June 2023, July 2023, June 2024, and July 2024, respectively. Precipitation over a 10-year period averaged 39.6 mm in June and 19.6 mm in July. Precipitation was 49.0, 6.9, 13.5, and 13.0 mm for June 2023, July 2023, June 2024, and July 2024, respectively. Vegetation consists of shrubs including mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle), antelope bitterbrush (Purshia tridentata [Pursh] DC.), yellow rabbitbrush (Chrysothamnus viscidiflorus [Hook.] Nutt.), threetip sagebrush (A. tripartita Rydb.), and spineless horsebrush (Tetradymia canescens DC.). Grass and grass-like species include Sandberg bluegrass (Poa secunda J. Presl), bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve), sedge (Carex L.), and Idaho fescue (Festuca idahoensis Elmer). Dominant forbs were parsnipflower buckwheat (Eriogonum heracleoides Nutt.), northwestern Indian paintbrush (Castilleja angustifolia [Nutt.] G. Don), longleaf (Erigeron corymbosus Nutt.), and littleleaf pussytoes (Antennaria microphylla Rydb.) [21]. As described by Moffet, Taylor, and Booth [21], stocking rates were light, with 15–30% of annual production being removed. A complete description of the grazing management is described elsewhere (see Calendar B) [3].

Data filtering

In 2023, complete data were available for 23 Rambouillet and 29 Katahdin ewes. Of the Rambouillet, 16 were in Band 1 and seven were in Band 2. Of the Katahdins, 17 were in Band 1 and 12 were in Band 2. Data loss was due to missing GPS collars, battery failure, or ewes being removed from the band for health reasons. Data collected from June 3 to July 9 were analyzed. In 2024, most of the GPS collars had battery failure, leaving five Rambouillet and five Katahdin ewes in the same band with complete data. Data collected from June 17 to July 6 were analyzed.

Data were extracted from microSD cards and loaded into Excel. Discernable GPS fix errors (outside of USSES boundaries) were removed from the dataset prior to being further analyzed in R [23]. The final number of records analyzed from Band 1 in 2023, Band 2 in 2023, and Combined Band in 2024 were 339,854, 195,782, and 56,063, respectively.

Statistical analysis

Data were formatted for further analysis using the lubridate [24] and sf [25, 26] packages in R. Data were analyzed separately for daytime hours (05:00 to 21:00 h, MDT) and nighttime hours (21:00 to 05:00 h, MDT). Dispersion was computed using the Euclidean distance of each ewe from the centroid of the study flock in meters [27]. Dispersion by breed and individual ewe within breed were analyzed. Dispersion was computed as

$$\sqrt {\left( {x_{2} - x_{1} } \right)^{2} + (y_{2} - y_{1} )^{2} ,}$$

where \({x}_{2}\) is the individual x coordinate, and \({x}_{1}\) is the mean of all x coordinates at a given time, \({y}_{2}\) is the individual y coordinate, and \({y}_{1}\) is the mean of all y coordinates at a given time. The Euclidean distance was computed as the square root of the sum of the squares of differences in both x and y coordinates. The Welch’s unequal variance t test was used to compare the means of the two breeds for distance from the study flock centroid. Cohen’s d statistic was computed to determine the effect size of the differences between the means [28]. The means of the study centroid for each breed were compared. The mean dispersion for each ewe was compared to the overall mean study flock centroid. Total daily distance traveled per ewe was computed by summing the distance traveled in meters for each daytime (16 h) and nighttime (8 h) period using the adehabitatLT package in R [29]. Mean total daily distance (daytime and nighttime) for each breed were compared using a t test. Cohen’s d was computed to determine the magnitude of the differences between the means. Mean total daily distance (daytime and nighttime) per ewe was compared to the overall mean total daily distance traveled using individual t tests.

Results

Distance from flock centroid

GPS fixes from 1 day from each study flock group were plotted to demonstrate how the GPS coordinates for all ewes by breed compared to the Rambouillet and Katahdin centroid on 6/15/2023 for Band 1 during the daytime (Fig. 1a) and nighttime (Fig. 1b), on 6/30/2023 for Band 2 during the daytime (Fig. 2a) and nighttime (Fig. 2b), and on 6/30/2024 for the Combined Band in 2024 during the daytime (Fig. 3a) and nighttime (Fig. 3b).

Fig. 1
figure 1

GPS coordinates for Katahdin and Rambouillet ewes compared to the mean centroid for each breed. GPS coordinates (x and y) for Band 1 for Katahdin (K; green) and Rambouillet (R; orange) ewes on 6/15/2023 for a) daytime hours from 05:00 to 21:00 (MDT) and b) nighttime hours from 21:00 to 05:00 (MDT) compared to the mean centroid for each breed

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Fig. 2
figure 2

GPS coordinates for Katahdin and Rambouillet ewes compared to the mean centroid for each breed. GPS coordinates (x and y) for Band 2 for Katahdin (K; green) and Rambouillet (R; orange) ewes on 6/30/2023 for a) daytime hours from 05:00 to 21:00 (MDT) and b) nighttime hours from 21:00 to 05:00 (MDT) compared to the mean centroid for each breed

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Fig. 3
figure 3

GPS coordinates for Katahdin and Rambouillet ewes compared to the mean centroid for each breed. GPS coordinates (x and y) for the Combined Band in 2024 for Katahdin (K; green) and Rambouillet (R; orange) ewes on 6/30/2024 for a) daytime hours from 05:00 to 21:00 (MDT) and b) nighttime hours from 21:00 to 05:00 (MDT) compared to the mean centroid for each breed

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For Band 1 in 2023, the mean distance from the centroid of the study flock was 120.4 (SE = 1.7) meters for Katahdin and 113.9 (SE = 1.7) meters for Rambouillet during the daytime (Fig. 4a and b) and 24.8 (SE = 1.2) meters for Katahdin and 24.5 (SE = 0.4) meters for Rambouillet during the nighttime (Fig. 5a and b). The means for these two breeds were significantly different (P < 0.05) during the daytime but not at nighttime. For Band 2 in 2023, the mean distance from the centroid of the study flock was 492.3 (SE = 13.8) meters for Katahdin and 546.8 (SE = 19.5) meters for Rambouillet during the daytime (Figs. 6a and b) and 441.4 (SE = 15.7) for Katahdin and 478.4 (SE = 20.8) meters for Rambouillet at nighttime (Figs. 7a and b). The means for the breeds were significantly different from each other (P < 0.05) both during the daytime and nighttime. In 2024, the mean distance from the study flock centroid was 231.2 (SE = 12.4) meters for Katahdin and 225.9 (SE = 15.8) meters for Rambouillet during the daytime (Figs. 8a and b) and 88.5 (SE = 8.7) meters for Katahdin and 80.1 (SE = 6.0) for Rambouillet at nighttime (Figs. 9a and b). The breed means were not significantly different (P > 0.05) either during the daytime or nighttime. Although significant differences were found, the effect size was small for all breed means across all study groups. In summary, dispersion from the study flock centroid was higher for the Katahdin breed in Band1 in 2023, higher for the Rambouillet breed in Band 2 in 2023, and similar for both breeds in 2024, but the magnitude of these differences was small.

Fig. 4
figure 4

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet). For Band 1 from June 3 to July 9, 2023 for daytime hours from 05:00 to 21:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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Fig. 5
figure 5

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet).For Band 1 from June 3 to July 9, 2023 for nighttime hours from 21:00 to 05:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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Fig. 6
figure 6

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet). For Band 2 from June 3 to July 9, 2023 for daytime hours from 05:00 to 21:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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Fig. 7
figure 7

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet). For Band 2 from June 3 to July 9, 2023 for nighttime hours from 21:00 to 05:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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Fig. 8
figure 8

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet). For the combined band in 2024 from June 17 to July 6, 2024 for daytime hours from 05:00 to 21:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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Fig. 9
figure 9

Mean distance from the centroid of the flock by breed (Katahdin and Rambouillet). For the combined bands in 2024 from June 17 to July 6, 2024 for nighttime hours from 21:00 to 05:00, a) mean distance (meters) from the centroid of the flock for Katahdin (K; green) and Rambouillet (R; orange) by date, and b) mean GPS coordinates (x and y) for Katahdin (K; green) and Rambouillet (R; orange) ewes

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The mean dispersion from the study flock centroid was computed for each ewe and evaluated for significance. For Band 1 in 2023, there were three Rambouillet ewes that were significantly closer to the study flock centroid (P < 0.05) and one Katahdin ewe that was significantly farther away from the study flock centroid (P < 0.05). Based on the GPS coordinates, the Katahdin ewe (Y0211) strayed away from the flock for ~ 14 h on June 7 before rejoining the flock. In Band 2 in 2023, there were four Katahdin ewes that were significantly closer to the flock centroid (P < 0.05). In 2024, no ewes were significantly different from the overall mean flock centroid (P > 0.05).

Daily distance traveled

For Band 1 in 2023, the mean daily distance traveled for all ewes averaged 9,761 (SE = 53) meters during the daytime and 2,309 (SE = 32) at nighttime. The Katahdin ewes averaged 9,723 (SE = 75) meters and the Rambouillet ewes averaged 9,801 (SE = 75) meters during the daytime (Fig. 10a) and the Katahdin ewes averaged 2,280 (SE = 44) meters and the Rambouillet ewes averaged 2,340 (SE = 46) meters at nighttime (Fig. 10b). The means for the breeds were not significantly different (P > 0.05) from each other for total daily distance traveled for either daytime or nighttime. For Band 2 in 2023, the mean daily distance traveled for all ewes was 7,641 (SE = 103) meters during the daytime and 1,842 (SE = 27) at nighttime. The Katahdin ewes averaged 7,465 (SE = 129) meters and the Rambouillet ewes averaged 7,943 (SE = 170) meters during the daytime (Fig. 11a) and the Katahdin ewes averaged 1,787 (SE = 34) meters and the Rambouillet ewes averaged 1,938 (SE = 44) meters at nighttime (Fig. 11b). The Rambouillet ewes had a significantly higher total daily distance than the Katahdin ewes for both daytime and nighttime (P < 0.05). In 2024, the mean daily distance traveled for all ewes was 10,814 (SE = 200) meters during the daytime and 2,741 (SE = 78) meters at nighttime. The Katahdin ewes traveled an average of 10,386 (SE = 277) meters, while the Rambouillet ewes traveled an average of 11,242 (SE = 284) meters during the daytime (Fig. 12a) and the Katahdin ewes traveled an average of 2,633 (SE = 88) meters and the Rambouillet ewes traveled an average of 2,848 (SE = 120) meters at nighttime (Fig. 12b). The difference in daily travel was significantly higher for the Rambouillet both during the day and at night (P < 0.05). Even though significant differences were found for total daily distance traveled between breeds, the magnitudes of the differences, as measured by Cohen’s d, were small.

Fig. 10
figure 10

Boxplots by breed (Katahdin and Rambouillet) for total daily distance traveled. Boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for Band 1 from June 3 to July 9, 2023 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Fig. 11
figure 11

Boxplots by breed (Katahdin and Rambouillet) for total daily distance traveled. legend. Boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for Band 2 from June 3 to July 9, 2023 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Fig. 12
figure 12

Boxplots by breed (Katahdin and Rambouillet) for total daily distance traveled. Boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for the Combined Bands from June 17 to July 6, 2024 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Individual ewe daily distance traveled was compared to the mean daily distance traveled for the overall study group. For Band 1 in 2023, there were two Rambouillet ewes and one Katahdin ewe that traveled significantly more (P < 0.05) and one Rambouillet ewe and four Katahdin ewes that traveled significantly less (P < 0.05) than the overall mean daily distance (Fig. 13). For Band 2 in 2023, three Rambouillet ewes and three Katahdin ewes had a significantly greater daily distance traveled than the overall mean (P < 0.05). There were four Katahdins that traveled significantly less (P < 0.05) than the overall mean daily distance (Fig. 14). In 2024, one Rambouillet ewe traveled significantly more (P < 0.05) and one Katahdin ewe that traveled significantly less than the overall mean daily distance traveled (P < 0.05; Fig. 15).

Fig. 13
figure 13

Boxplots by individual for total daily distance (meters) traveled. Individual boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for Band 1 from June 3 to July 9, 2023 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Fig. 14
figure 14

Boxplots by individual for total daily distance traveled. Individual boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for Band 2 from June 3 to July 9, 2023 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Fig. 15
figure 15

Boxplots by individual for total daily distance traveled. Individual boxplots for Katahdin (green) and Rambouillet (orange) for total daily distance (meters) traveled for the Combined Bands from June 17 to July 6, 2024 for a) daytime hours from 05:00 to 21:00 and b) nighttime hours from 21:00 to 05:00

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Discussion

Large U.S. West range-based systems include large pastures often unfenced with sparse forage and limited water resources. Furthermore, predator pressure is usually greater and much more diverse compared with U.S. Midwest and East pasture systems. Generally, sheep are managed under a continuous (24/7) herded system in large bands (500 – 2,000 head) by a single herder with working animals (herding dogs, guardian dogs, and horses). Rather than a fence providing the grazing boundary, herders dictate daily grazing movements across extensive landscapes, a system relatively foreign to the Katahdin breed. Such management requires the entire flock to stay in close proximity, exhibiting a strong flocking behavior. Small numbers of sheep forming isolated groups away from the main flock result in greater predation, lost sheep, and increased labor inputs to return stray sheep to the flock.

Determining the suitability of the Katahdin breed for U.S. West extensive range-based systems is somewhat problematic considering that limited to no genetic selection occurred for flocking instinct, range hardiness, response to herded management, and ability to travel long distances for feed and water. The breed was developed under small-pasture management systems where fences define grazing boundaries. Forages in these systems are usually very productive requiring minimal travel effort of sheep to meet daily nutritional needs. Genetic selection of Katahdin sheep was mostly focused on growth performance, hair shedding, parasite resistance, and reproductive success.

To address the research objective, Katahdin and Rambouillet study ewes fitted with GPS collars were uniquely managed within herded, range-based production bands (800–1000 ewes with lambs) of sheep. The bands consisted of Targhee, Polypay, and Rambouillet breed ewes, which were specifically developed and/or selected to perform under continuous herded management while grazing extensive rangelands. The use of GPS collars allowed estimation of a flock centroid and daily distance traveled. The two measures were not dependent upon each other, because some ewes stayed close to the flock yet covered more distance within that space, while others ventured farther from the flock but did not travel as many meters per day. Ewes from Band 1 in 2023 that represent low or high distance from the study flock centroid paired with low or high total daily distance are shown in Fig. 16.

Fig. 16
figure 16

Mean distance from flock centroid and total daily distance traveled for selected Katahdin ewes. Mean distance from flock centroid (meters) and total daily distance traveled (meters) for selected Katahdin ewes that are low distance from the flock centroid and low total daily distance traveled (Y0245), high distance from the flock centroid and low total daily distance traveled (Y0080), low distance from the flock centroid and high total daily distance traveled (Y0219), and high distance from the flock centroid and high total daily distance traveled (Y0237) for Band 1 in 2023

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Katahdin and Rambouillet breeds differed for distance from the study flock centroid and total daily distance traveled. However, the response varied by study group and year, with no discernable trend of one breed separating from the other. The effect size was determined to be small, providing further evidence that the differences were due to the large quantity of GPS data rather than actual breed differences. In a study comparing a locally adapted cattle breed to a commercial cattle breed, both distance from the centroid of the herd and daily distance traveled were higher for the adapted cattle breed [30], indicating a willingness to seek out available forage. Unlike cattle, where moving away from the herd is considered a positive attribute that contributes to grazing distribution [31], sheep survival depends upon remaining close to the flock and not on the periphery [32]. Similar to cattle, daily distance traveled by sheep, regardless of proximity to the flock centroid, may indicate a willingness to seek out preferred forage. In a study using visual observations, differences in distance traveled were evident between Merino and Dorper sheep in South Africa, but the differences were dependent whether the grazing conditions were intensive or extensive [33]. The similarities in flocking behavior between the Rambouillet and Katahdin ewes suggested that the Katahdin breed utilized the extensive range environment similar to the Rambouillet, not venturing away or separating from the flock.

At the individual ewe level, there were ewes from each breed that were significantly closer and farther away from the overall flock centroid, but there was no consistent trend by breed. Similarly, there were ewes from each breed that traveled more daily distance or less daily distance than the mean of the flock, but there was no clear trend by breed. The lack of a consistent response indicative of Katahdin ewes separating from the flock was not observed. Of note, distance traveled in sheep has been reported as both moderately heritable and repeatable [34], indicating that genetic selection can be made for this trait. Other studies used a similar number of GPS collars or other GPS data loggers for sheep studies, including 12–18 per pasture [35], five ewes from a flock of 200–300 ewes [36], and 15 ewes per pasture [37], but a much larger data set consisting of 422 sheep was used to estimate heritability and repeatability for daily distance traveled [34]. Other traits that could impact flockability or sheep behavior that have been reported to have a genetic component include temperament [38], gregariousness [39], and fearfulness [39]. Boissy, Bouix [39] suggested genetic selection for increased gregariousness and decreased fearfulness could have an economic, ethical, and productivity impact.

While this study provided observations to detect differences in individual animals and across breeds, additional animals and repeated measures on the same animals over multiple years would be required to estimate heritability and repeatability for flockability. Additionally, keeping study ewes together in the sub-groups in early spring would provide data over a longer period of time. Enhanced GPS tracking methods which would allow for accessing data in real time or near real time would avoid the data loss due to battery failure in the current study. This is challenging in extensive grazing environments, but can be overcome with technology such as LoRa, which allows data to be transferred across a long range using low power [40]. Pairing the data with other measures of productivity (ewe weight, ewe body condition, lamb survival, and lamb weaning weights) are planned. Continued GPS monitoring of these ewes over their lifetime would provide further insight into the long-term adaptation of the Katahdin sheep to an extensive range environment.

Conclusion

The Katahdin breed was similar in flockability to the range-adapted Rambouillet breed, indicating that the Katahdin breed flocking behavior is well suited for herded grazing in extensive rangeland environments. While significant differences were identified by breed for distance from the flock centroid and total daily distance traveled, differences did not consistently favor one breed over the other. Future analyses of production performance are planned and will provide further insight into the suitability of the Katahdin breed for an extensive range environment. The present study indicated that the Katahdin exhibits favorable behavioral characteristics to perform well in a large range flock and provides an opportunity for Western U.S. producers interested in incorporating this breed into their flock.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

SE:

Standard error

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Acknowledgements

We thank John Bergeron and Andrew Hess for proving the R code used for the centroid analyses. We thank the U.S. Sheep Experiment Station animal care and technical staff for managing the GPS collars, with extra appreciation for meticulous equipment and data management by Jasmine Harris. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. The USDA is an equal opportunity provider and employer.

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  1. Range Sheep Production Efficiency Research Unit, USDA, ARS, Dubois, ID, USA

    Carrie S. Wilson, J. Bret Taylor, Jonathan W. Spiess & Hailey Wilmer

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Contributions

CSW analyzed and interpreted the data and wrote the initial manuscript. JBT designed the Katahdin and Rambouillet experiment and contributed to the interpretation of results. HW and JWS contributed to the interpretation of results. All authors read and approved the final manuscript.

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Correspondence to Carrie S. Wilson.

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The USSES Institutional Animal Care and Use Committee (IACUC) approved all husbandry practices and experimental procedures used in this study.

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Wilson, C.S., Taylor, J.B., Spiess, J.W. et al. Comparison of the flocking behavior of Katahdin and Rambouillet sheep breeds in an extensive range environment using GPS technology. Anim Biotelemetry 13, 7 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s40317-025-00404-6

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Keywords

Animal Biotelemetry

ISSN: 2050-3385