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Comparison of endoparasite abundance and species richness of two Roosevelt elk herds in northern California

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FULL RESEARCH ARTICLE

Scarlett A. Stromer1,2, Carrington K. Hilson1, and Richard N. Brown2

1 California Department of Fish and Wildlife, Region 1, 619 2nd Street, Eureka, CA 95501, USA
2 California Polytechnic University, Humboldt, Wildlife Department, 1 Harpst Street, Arcata, CA 95521, USA

Corresponding Author: scarlett.stromer@wildlife.ca.gov

Published 12 October 2022 • http://www.doi.org/10.51492/cfwj.108.14

Abstract

Roosevelt elk (Cervus canadensis roosevelti) have historically populated the Pacific Northwest from the Olympic Peninsula to the south of San Francisco Bay, and several management actions have supported restoring elk into parts of this historic range. In 1982, 17 Roosevelt elk were translocated from Gold Bluffs Beach State Park to Sinkyone Wilderness State Park. In 2020, the Sinkyone elk herd was observed to have lower body condition scores and poor coat conditions in comparison to the Gold Bluffs Beach elk herd. Therefore, the objectives of this study were to investigate the difference in health between the two herds. Fecal samples were collected (n = 20) from each herd to measure species richness and abundance of parasites. We determined there was a significant difference in species richness and abundance of parasite eggs between the two herds. The Sinkyone herd’s overall higher endoparasite load may be attributed to a low immune response due to low nutrition but, causation is unknown.

Key words: abomasal parasites, California, Cervus canadensis roosevelti, fecal analysis, Gold Bluffs Beach, Roosevelt elk, Sinkyone Wilderness

Citation: Stromer, S. A., C. K. Hilson, and R. N. Brown. 2022.  Comparison of endoparasite abundance and species richness of two Roosevelt elk herds in northern California. California Fish and Wildlife Journal 108:e15.
Editor: Kristin Denryter, Wildlife Branch (former), Alaska Department of Fish and Game (current)
Submitted: 29 December 2021; Accepted: 3 March 2022
Copyright: ©2022, Stromer et al. This is an open access article and is considered public domain. Users have the right to read, download, copy, distribute, print, search, or link to the full texts of articles in this journal, crawl them for indexing, pass them as data to software, or use them for any other lawful purpose, provided the authors and the California Department of Fish and Wildlife are acknowledged.
Funding: The California Department of Fish and Wildlife provided a vehicle and funded this research with field collection supplies.
Competing Interests: The authors have not declared any competing interests.

Introduction

Within the state of California, Roosevelt elk (Cervus canadensis roosevelti) inhabit portions of Humboldt, Del Norte, Mendocino, Siskiyou, and Trinity counties due to reintroduction efforts and natural range expansion (CDFW 2018). In March 1982, 17 Roosevelt elk from Gold Bluffs Beach, within Prairie Creek Redwood State Park, Humboldt County, were translocated to a similar habitat in Sinkyone Wilderness State Park in Mendocino County (CDFW 2018; California State Park 2016). This herd of elk continues to persist within the Sinkyone Wilderness State Park in the BLM King Range National Conservation Area (Wengert 2000). 

Cervids can experience different effects from endoparasites, depending on the number of parasites and the species present. Gastrointestinal (GI) nematodes have been found to cause deterioration of health, weight loss in young cervids, and cause reproductive disorders in adults; however other researchers have concluded that some GI nematodes’ relations with cervids result in subclinical infections (Goossens et al. 2005). Abomasal parasites such as species within the family Trichostrongylidae can cause blood loss and damage to the abomasal lining, including inflammation, edema, and necrosis (Botzler and Brown 2014). These parasites can lead to diarrhea and emaciation (Botzler and Brown 2014), rough hair coat, and severe infections can result in death (Chisolm 2006). Infections of Eimeria spp. can be subclinical or clinical, depending on the species of parasite and age of the host, with bloody diarrhea being the main sign associated with coccidial infections (Chisolm 2006).

In 2000, Wengert found that a low percentage of the elk in Sinkyone had good body condition and identified eight species of helminths: Trichuris sp., Capillaria sp., trichostrongylids #1, #2, and #3, Mashallagia sp., and Nematodirus sp. and one species of Eimeria from fecal analysis. In 2020 there were additional observations of thin elk with poor coat conditions in the Sinkyone herd, especially compared to the herd at Gold Bluffs Beach. Poor coat and body conditions can be related to an elk’s overall health and immune system. Nutrition contributes to an animal’s immune response and resistance to parasites (Greer 2008). This difference in health between the two herds could be due to environmental differences such as population density (Goossens et al. 2005), inadequate macronutrients (Cook et al. 2016), or endoparasite prevalence (Greer 2008). Therefore, our objective was to investigate the difference in health between the two herds of elk using fecal analysis. Due to a difference in coat conditions and how that interferes with overall immune health, we hypothesized that the Sinkyone herd would have a higher prevalence and species richness of helminths eggs and oocysts when compared to those in the Gold Bluffs Beach herd. 

Methods

Study Area

The study was conducted in two locations: Gold Bluffs Beach State Park, Humboldt County, (41.332, –124.081; Fig. 1) and Sinkyone Wilderness State Park, Mendocino County (39.9537, –123.9728; Fig. 2). 

Figure 1. Location of fecal pellet sampling (n = 20) and individual observation of Roosevelt elk in Gold Bluffs Beach State Park (Humboldt County), CA, USA, from January to February 2020. Home range derived from two collared cow Roosevelt elk, Humboldt County, CA, USA. The home range was derived using kernel utilization distribution at 99% (low use), 95% (medium use), and 50% (high use). Image shows a map of the Gold Bluffs sample collection area. The edges of the Prairie Creek Redwood State Park, where Gold Bluffs Beach is located, are shown in green. Areas of high use by elk are shown in red, areas of medium use are shown in orange, and areas of low use are shown in yellow. All areas of use are along the coast on the eastern side of the park. Fecal collection points are shown by green dots. There are two clusters of fecal collection points in the coastal areas used by elk, one at the southern end of the park and one halfway between the southernmost and northernmost part of the park.
Figure 1. Location of fecal pellet sampling (n = 20) and individual observation of Roosevelt elk in Gold Bluffs Beach State Park (Humboldt County), CA, USA, from January to February 2020. Home range derived from two collared cow Roosevelt elk, Humboldt County, CA, USA. The home range was derived using kernel utilization distribution at 99% (low use), 95% (medium use), and 50% (high use).
Figure 2. Location of fecal pellet sampling (n = 20) and individual observation of Roosevelt elk in Sinkyone Wilderness State Park (Mendocino County), CA, USA, from February to March 2020. Home range derived from two collared cow Roosevelt elk, Mendocino County, CA, USA. The home range was derived using kernel utilization distribution at 99% (low use), 95% (medium use), and 50% (high use). Image shows a map of the Sinkyone Wilderness sample collection area. The edges of the Sinkyone Wilderness State Park are shown in green. Areas of high use by elk are shown in red, areas of medium use are shown in orange, and areas of low use are shown in yellow. The areas of high use are along the coast on the northwestern side of the park. Areas of medium and low use cover the entire coast of the park. There are small areas of medium and low use scattered inland north of the park. Fecal collection points are shown by green dots. There are two clusters of fecal collection points in the area marked as high use along the northwest edge of the park on the coast.
Figure 2. Location of fecal pellet sampling (n = 20) and individual observation of Roosevelt elk in Sinkyone Wilderness State Park (Mendocino County), CA, USA, from February to March 2020. Home range derived from two collared cow Roosevelt elk, Mendocino County, CA, USA. The home range was derived using kernel utilization distribution at 99% (low use), 95% (medium use), and 50% (high use).

Both locations’ climate varies considerably, with high precipitation and moderate temperatures averaging from 7–9°C in the months of February to March 2020 (NOAA 2022). The coastal provinces receive more rainfall than any other part of California, sustaining a diverse ecosystem of flora and fauna (CDFW 2015; California State Park 2021). Gold Bluffs Beach is a 10 mile stretch of coastline ranging from sea level to 180 meters in elevation, surrounded by soft serpentine soil and sandy beaches, with grass-covered dunes, groves of red alder (Alnus rubra), old-growth coastal redwoods (Sequoia sempervirens), and mixed conifer forests (Bowyer 1981; CDFW 2015; Humboldt California’s Redwood Coast 2019). The Sinkyone Wilderness State Park is a 60-mile stretch of coastline ranging from sea level to 425 m in elevation and is mostly composed of shrubs and grassland interspersed with Douglas fir (Pseudotsuga menziesii). Both locations support terrestrial communities of Roosevelt elk, black-tailed deer (Odocoileus hemionus), black bear (Ursus americanus), mountain lions (Pumas concolor), coyotes (Canis latrans), and bobcats (Lynx rufus) (CDFW 2015). Within the Sinkyone Wilderness State Park, marine mammals can be spotted along the shoreline, such as Northern elephant seals (Phoca leonine), California sea lions (Zalophus californianus), and harbor seals (Phoca vitulina) (California State Parks 2021).

Locating the Elk 

California Department of Fish and Wildlife (CDFW) personnel fitted GPS collars on two cow elk in Sinkyone (on 24 January 2019) and two cow elk at Gold Bluffs Beach (on 9 March 2017 and 20 November 2019). These capture efforts were found to be ethical and approved by Institutional Animal Care and Use Committee (IACUC) (15/16.W.96-A). We located elk with GPS location data from the collars paired with radio telemetry. Once the elk were located, all observations of elk defecating were performed with an unaided eye or by using 10×42 binoculars at 5–100 m (Bowyer 1981). 

Fecal Collection 

This research was approved by CDFW and IACUC (16/17.W.46-E). We conducted the study from 24 January to 20 March 2020, during which fecal samples from 20 individuals were obtained from each herd over the course of two visits per location (Figs. 1 and 2). To ensure that samples were fresh and from different elk, five samples (4 females and 1 calf) from individual elk in the Gold Bluffs Beach herd and nine samples (7 females, 1 male, and 1 calf) from individual elk in the Sinkyone herd were collected after observing the elk defecating. All other samples were collected opportunistically with an internal temperature above 10°C and were at least three or more meters distant from another sample (Turner and Getz 2010). Fecal samples were examined visually for parasites, blood, and mucous before being placed in their own individual sterile 4-oz Whirl Pak bag with the air removed to preserve the parasites (Zajac and Conboy 2006). Each fecal sample was placed on ice to prevent helminth eggs from hatching (Nielsen et al. 2010).

Fecal Smear and Floatation 

Samples were refrigerated at the Cal Poly, Humboldt Wildlife Disease Lab in Arcata, CA, USA, for immediate testing. Fecal floats were performed using ~1.0 g of feces in a Fecalyzer® (Vétoquinol USA Inc., Buena, NJ, USA). Fecal smears were performed by placing a direct smear of feces and several drops of Fecasol® (Sodium nitrate solution, Vétoquinol USA Inc., Buena, NJ, USA) onto a glass slide with a coverslip (Zajac and Conboy 2006). Helminths and oocysts were identified using a compound microscope (Zajac and Conboy 2006) and measured using a micrometer (González-Ruiz and Bendall 1995). All identifications were confirmed by R. Brown.

Data Analysis

Due to eggs being difficult to differentiate to species without molecular methods, we used scatter plots to distinguish the difference in the size of eggs we were finding.  The size of Eimeria oocysts ranged from 20 µm to 48 µm. We were able to categorize Eimeria spp. oocysts into five different species groups (Fig. 3). 

Figure 3. Eimeria spp. size chart from fecal samples collected from Sinkyone Roosevelt elk (dark grey) and Gold Bluffs Beach elk (grey). Eimeria sp. #1 (20 μm) Eimeria sp. #2 (24 μm) Eimeria sp. #3 (27–31 μm) and Eimeria sp. #4 (45–48 μm), Eimeria sp. #5 (34–38 μm). All samples were collected from Sinkyone Wilderness State Park, CA, USA, and Gold Bluffs Beach State Park, CA, USA, from January to March 2020. Image shows a dot plot graph with an x axis titled Total Eimeria oocysts and a y axis titled Length of oocysts in micrometers. There are eleven oocysts of Eimeria sp. #1 (20 micrometers in length), all of which were collected from Sinkyone Roosevelt elk, ten oocysts of Eimeria sp. #2 (24 micrometers in length), one of which was collected from Gold Bluffs Beach elk and the other nine of which were collected from Sinkyone Roosevelt elk, eight oocysts of Eimeria sp. #3 (between 27 and 31 micrometers in length, one of which was collected from Gold Bluffs Beach elk and the other seven of which were collected from Sinkyone Roosevelt elk, four oocysts of Eimeria sp. #5 (between 34 and 38 micrometers in length), all of which were collected from Gold Bluffs Beach Elk, and two oocysts of eimeria Sp. #4 (between 45 and 48 micrometers in length), both of which were collected from Sinkyone Roosevelt elk.
Figure 3. Eimeria spp. size chart from fecal samples collected from Sinkyone Roosevelt elk (dark grey) and Gold Bluffs Beach elk (grey). Eimeria sp. #1 (20 μm) Eimeria sp. #2 (24 μm) Eimeria sp. #3 (27–31 μm) and Eimeria sp. #4 (45–48 μm), Eimeria sp. #5 (34–38 μm). All samples were collected from Sinkyone Wilderness State Park, CA, USA, and Gold Bluffs Beach State Park, CA, USA, from January to March 2020.

Similarly, Strongylid spp. helminths size ranged from 31 µm to 100 µm. We categorized Strongylid spp. helminths into five species groups (Fig. 4). 

Figure 4. Strongylid spp. egg size chart from fecal samples collected from Sinkyone Roosevelt elk (dark grey) and Gold Bluffs Beach elk (grey): Strongylid sp. #1 (31–41 μm), Strongylid sp. #2 (52–59 μm), Strongylid sp. #3 (69 μm), Strongylid sp. #4 (79–93 μm), and Strongylid sp. #5 (97–100 μm). All samples were collected from Sinkyone Wilderness State Park, CA, USA, and Gold Bluffs Beach State Park, CA, USA, from January to March 2020. Image shows a dot plot graph with an x axis titled Total Strongylid helminths and a y axis titled Length of helminths in micrometers. There are four helminths of Strongylid sp. #1 (between 31 and 41 micrometers in length), one of which was collected from Sinkyone Roosevelt elk and three of which were collected from Gold Bluffs Beach elk, four helminths of Strongylid sp. #2 (between 52 and 59 micrometers in length), two of which were collected from Sinkyone Roosevelt elk and two of which were collected from Gold Bluffs Beach elk, four helminths of Strongylid sp. #3 (69 micrometers in length), eighteen helminths of Strongylin sp. #4 (between 79 and 93 micrometers in length), seven of which were collected from Sinkyone Roosevelt elk and eleven of which were collected from Gold Bluffs Beach elk, and two helminths of Strongylid sp. #5 (between 97 and 100 micrometers in length), both of which were collected from Sinkoyne Wilderness elk. All helminths of Strongylid sp. #4 collected from Sinkyone Roosevelt elk are longer than those of the same species collected from Gold Bluffs Beach elk.
Figure 4. Strongylid spp. egg size chart from fecal samples collected from Sinkyone Roosevelt elk (dark grey) and Gold Bluffs Beach elk (grey): Strongylid sp. #1 (31–41 μm), Strongylid sp. #2 (52–59 μm), Strongylid sp. #3 (69 μm), Strongylid sp. #4 (79–93 μm), and Strongylid sp. #5 (97–100 μm). All samples were collected from Sinkyone Wilderness State Park, CA, USA, and Gold Bluffs Beach State Park, CA, USA, from January to March 2020.

A Mann-Whitney U test was used to evaluate the medians of the abundance of helminth eggs and Eimeria spp. oocysts, and to compare species richness between each herd of elk. Finally, we calculated the prevalence of each parasite by dividing the number of infected elk by the total sampled, and the parasite genera per elk were calculated by dividing elk infected by 0, 1, 2, 3, or 4 genera by the total sampled. 

Results

Parasites

Overall, 13 species of parasites were identified from the Sinkyone herd, including four species of Eimeria, eight nematodes, and one species of fluke. The Gold Bluffs Beach herd had 10 species of parasites present, including three species of Eimeria spp. and seven species of nematodes. The Sinkyone herd had a greater species richness than the Gold Bluffs Beach herd (U = 123, P = 0.033). 

The abundance of parasites was higher in the Sinkyone herd than in the Gold Bluffs Beach herd (U = 88.5, P = 0.003); 275 eggs or oocysts were found in samples from the Sinkyone herd, and 66 eggs or oocysts were found in samples from the Gold Bluffs Beach herd. However, one cow from the Sinkyone herd was an outlier with 138 helminth eggs counted, and her sample was omitted from the analysis of abundance.

Prevalence for each type of parasite was determined for all samples (n = 20 from each herd). Sinkyone had a higher prevalence of seven species: Eimeria sp. #1, #2, #3, and #4, Toxocara sp., strongylid sp. #5., and Fasciola hepatica. Gold Bluffs Beach had a higher prevalence of four species: Eimeria sp. #5, strongylid sp. #1 and #4, and Nematodirus sp. Elk at both locations had a similar prevalence of Capillaria sp. and strongylid sp. #2 and #3 (Fig. 5). 

Figure 5. Prevalence of parasites estimated from forty Roosevelt elk fecal samples collected from Sinkyone Wilderness State Park, Mendocino County, CA, USA, (n = 20) (black lines), and Gold Bluffs Beach State Park, Humboldt County, CA, USA, (n = 20) (gray lines). Image shows a bar graph with an x axis listing all species of parasites discussed in this paper and a y axis titled Prevalence ranging from 0 to 0.6. Emieria sp. 1 has an estimated prevalence between 0.5 and 0.6 in Sinkyone Roosevelt elk and an estimated prevalence of 0 in Gold Bluffs Beach elk, Emieria sp. 2 has an estimated prevalence of 0.4 in Sinkyone Roosevelt elk and an estimated prevalence between 0 and 0.1 in Gold Bluffs Beach elk, Emieria sp. 3 has an estimated prevalence between 0.3 and 0.4 in Sinkyone Roosevelt elk and an estimated prevalence between 0 and 0.1 in Gold Bluffs Beach elk, Emieria sp. 4 has an estimated prevalence between 0.1 and 0.2 in Sinkyone Roosevelt elk and an estimated prevalence of 0 in Gold Bluffs Beach elk, Emieria sp. 5 has an estimated prevalence of 0 in Sinkyone Roosevelt elk and an estimated prevalence between 0.2 and 0.3 in Gold Bluffs Beach elk, Strongylid sp. 1 has an estimated prevalence between 0 and 0.1 in Sinkyone Roosevelt elk and an estimated prevalence of 0.1 in Gold Bluffs Beach elk, Strongylid sp. 2 has an estimated prevalence of 0.1 in both Sinkyone Roosevelt elk and in Gold Bluffs Beach elk, Strongylid sp. 3 has an estimated prevalence of 0.1 in both Sinkyone Roosevelt elk and in Gold Bluffs Beach elk, Strongylid sp. 4 has an estimated prevalence between 0.4 and 0.5 in Sinkyone Roosevelt elk and an estimated prevalence between 0.5 and 0.6 in Gold Bluffs Beach elk, Strongylid sp. 5 has an estimated prevalence of 0.1 in Sinkyone Roosevelt elk and an estimated prevalence of 0 in Gold Bluffs Beach elk, Capillaria sp. has an equal estimated prevalence between 0.2 and 0.3 in both Sinkyone Roosevelt elk and in Gold Bluffs Beach elk, Nematodirus sp. has an estimated prevalence between 0.1 and 0.2 in Sinkyone Roosevelt elk and an estimated prevalence of 0.3 in Gold Bluffs Beach elk, Toxocara sp. has an estimated prevalence between 0.2 and 0.3 in Sinkyone Roosevelt elk and an estimated prevalence between 0 and 0.1 in Gold Bluffs Beach elk, and Fasicola hepitica has an estimated prevalence between 0 and 0.1 in Sinkyone Roosevelt elk and an estimated prevalence of 0 in Gold Bluffs Beach elk.
Figure 5. Figure 5. Prevalence of parasites estimated from forty Roosevelt elk fecal samples collected from Sinkyone Wilderness State Park, Mendocino County, CA, USA, (n = 20) (black lines), and Gold Bluffs Beach State Park, Humboldt County, CA, USA, (n = 20) (gray lines).

There was a higher percentage of samples from Sinkyone with multiple species of parasites; 50% of the samples yielded 2–3 parasite species, 4 species were identified in 20%, and 5 species were identified in 10% of samples. In comparison, only 1–2 species of parasites were found in 70% of the samples from Gold Bluffs Beach, and no individual was found with more than 4 species (Table 1).

Table 1. The percentage of Roosevelt elk with evidence of intestinal parasitism and the number of species detected from fecal pellets collected from Sinkyone Wilderness State Park (n = 20), Mendocino County, CA, USA, and Gold Bluffs Beach State Park (n = 20), Humboldt County, CA, USA from January to March 2020.

Table 1a. Sinkyone Herd

# of species# of elk infected% of herd
015%
1315%
2525%
3525%
4420%
5210%

Table 1b. Gold Bluffs Beach Herd

# of species# of elk infected% of herd
0210%
1630%
2840%
3210%
4210%
500%

Discussion

We determined that the Sinkyone herd had a higher species richness and parasite abundance when compared to the Gold Bluffs Beach herd, which supports our hypothesis. Other variables such as habitat use, nutrition, and density of the population could be a factor in the difference of abundance and species richness of parasites found, but causation is unknown.

Sinkyone elk had a higher prevalence of helminth eggs and Eimeria spp. oocysts, with one additional species of strongylid, compared to Gold Bluffs Beach. Wengert (2000) found a total of eight species of parasites in the Sinkyone herd: including Trichuris sp. and Marshallagia sp., which were not identified in this study. She reported a few genera of parasites found were no cause for alarm; however, parasitism of various helminths could affect population growth and herd health over the long term (Wengert 2000).

Comparing our findings to Wengert’s, we found 7 more parasite species than she did. This difference could be due to many environmental factors, such as the elk population in Sinkyone has grown since 2000, allowing for easier disease transmission, or perhaps climate change is creating favourable conditions for the parasites. These probable changes could be investigated in the future.

Wengert (2000) also found low body scores from the Sinkyone herd. Body condition can be affected by many variables, including parasites and herd size relative to carrying capacity; high abomasal parasite counts have been used to indicate that white-tailed deer herds are beyond their carrying capacity (Eve and Kellogg 1977). Other factors also affect body condition, and no correlation was found between abomasal parasite load and body condition of black-tailed deer from three locations in coastal and inland Humboldt County (Botlzer 1979). Recent studies show that northern ungulate species are reliant on summer nutrition and nitrogen rich plants, which provide a digestible protein, and energy which can result in a higher fecundity rate and higher lean body mass (Cook et al. 2016, Rowland et al. 2018, and McArt et al. 2009).

More work is needed to determine which factors, including population density relative to carrying capacity, macronutrients, climate change, endoparasites, or other diseases, may be contributing to the health differences of these elk herds. Our sample size was small, making it likely that some parasites were missed. Helminth eggs are not shed consistently by individuals throughout the day, so we recommend collection of fecal samples in the morning when ungulates are active and grazing, which will increase the sample size of unique individuals. Additionally, parasites are shed inconsistently through the seasons and are typically more prevalent in the summer, and fall months (Eve and Kellogg 1977). We recommend testing parasite loads with a larger fecal sample size collected during the ideal time and seasons, performing necropsies with abomasal parasite counts to quantify parasite loads, and use of molecular methods to clarify the identification of parasites found. 

Management Implications

Herd health should be considered when managing populations of elk. Factors that increase overall endoparasite egg abundance, and species richness should be addressed, and management actions should be taken when necessary. Many factors affecting herd health and disease transmission are density-dependent, but, in locations without harvest, a reduction of herd size or an increase in available habitat should  be considered  a mechanism to decrease disease transmission.

Acknowledgments

We would like to thank CDFW and California State Parks for supporting this research and allowing access to their land to collect biological samples. We thank multiple field assistants, including A. Harper, H. Jones, and S. Lopez. Thank you, A. Harper, for performing home range analysis for the study area maps. CDFW provided a vehicle and funded this research with field collection supplies.

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