Geology topics

Saeideh Esmaeili

Publications and source records attributed to Saeideh Esmaeili.

8 recordsLinked to original sources

USGS2026

Growth patterns, sexual dimorphism, and seasonal body mass variation in Plains Zebra of the Serengeti region, Tanzania

Knowledge of growth patterns and physical properties of animals helps researchers assess population characteristics and health in the field. Information on age-specific body measurements and growth patterns is rare in ungulates because examining a large portion of a population is time-, budget-, and personnel-intensive in the wild. We collected age- and sex-specific body measurements from 442 Plains Zebra ( Equus quagga boehmi ) culled in the Serengeti region, Tanzania, between 1969 and 1971. The dataset contained 307 males and 133 females. We found that males were on average 2.8% larger than females in body measurements of heart girth, height at shoulder, neck-body length, hind foot length, and the body mass, indicating minimal sexual dimorphism in adult Plains Zebra. We used polynomial regression to explore the relationship between heart girth and body mass and applied third-degree polynomial regression models to predict body mass for 34 females and 115 males with recorded girth but missing body mass records. We applied 5 non-linear models—Gompertz, von Bertalanffy, Bertalanffy-Pütter, logistic, and Richards—to characterize sex-specific growth trajectories for each trait. Our results showed that different traits followed different growth patterns, with size asymptotes reached by ∼2 to 5 yr depending on trait and sex. Seasonal trends in adult body mass were also evaluated using generalized linear models incorporating sex and cyclical effects of day of year. While female body mass showed little seasonal variation, adult males exhibited a 16.9% increase in mass during the wet season, followed by a sharp decline, suggesting greater seasonal plasticity and energetic investment. Our work is one of the few studies on body size and growth in wild equids, which provides new information on age- and sex-specific growth trajectories for comparison across zebra subspecies over time and space.

Serengeti region↗

USGS2026

When the desert dries: Rainfall drives conflicts and conservation challenges for onager (Equus hemionus onager)

Increasingly, the conservation of large and wide-ranging animals is challenged by environmental variability, static boundaries of protected areas, and the expansion of human activities. The Critically Endangered Onager ( Equus hemionus onager ) exemplifies these issues in Qatrouiyeh National Park (QNP) and the surrounding Bahram-e-Goor Protected Area (BPA) in Iran. Using GPS telemetry data from 9 adult females tracked over 2 years, we examined seasonal patterns in movement and incursions into cultivated lands in 2017 and 2018. Net squared displacement analyses indicated that most individuals exhibited range-resident behavior with occasional nomadic movements, with no evidence for migration (i.e., predictable movements to and from distinct seasonal ranges). Both monthly home range size and monthly movement rate varied seasonally, peaking in late spring and early summer (May–July). Individual home ranges were between 257 and 1,928 km 2 , while the extrapolated population-level home range (718 km 2 ; 95% confidence interval = 276–1368) extended well outside QNP, covering large portions of the BPA. Occurrence distributions also expanded beyond the protected area into adjacent cultivated lands, highlighting the use of human-occupied areas by onagers. We recorded 2,285 (out of 72,168) GPS locations within cultivated lands and their surrounding 50 m buffer, with 60% of these incursions occurring immediately adjacent to QNP. Most incursions occurred at night and were strongly associated with both season and cumulative rainfall over the preceding 9 months. These findings emphasize how rainfall-driven variability in resource dynamics shapes the spatial distribution and behavior of onagers, thus elevating the risk of conflict with humans. The scale and seasonality of Onager movements highlight the need for flexible, landscape-level conservation strategies that extend beyond fixed park boundaries to encompass critical habitats and to mitigate conflict across the broader region.

Bahram-e-Goor Protected Area, Qatrouiyeh National ↗

USGS2026

Human dimensions and mountain sheep

We review components of the human dimension relationship between mountain sheep (bighorn sheep [Ovis canadensis] thinhorn [Ovis dalli]) and mankind. The relationships people hold with nature are incorporated into policymaking, regulation, and funding of wildlife management. Bighorn sheep experienced a massive decline in range and population size during the 19th century due to human occupation of foothills and overgrazing by domestic sheep. This encroachment led to significant habitat loss, unregulated harvesting, and the spread of diseases from domestic sheep to mountain sheep. Efforts to restore populations to their former ranges were influenced by the value of mountain sheep as recreational game species and for wildlife viewing. Restoration brought many bighorn populations into contact with people because the remaining habitat was already subjected to urban expansion. The population declines, fragmentation of habitat, and narrowing of bighorn ranges have had a profound effect on public opinion toward the species, shifting the animal from an accessible source of food through subsistence hunting to a species of conservation concern with limited harvest opportunities. Studies investigating the relationship between humans and mountain sheep have largely focused on the implications of human activities on mountain sheep, including conflict and disturbance, evolutionary pressure from selective hunting, attitudes toward the management of mountain sheep and relevant predator species, and human-wildlife conflict resulting from livestock disease spillover. Human attitudes are understudied. Although strides have been made in restoring mountain sheep populations and their habitats, the species’ population has been reduced compared to historical estimates and its original distribution. As a result, hunting for mountain sheep is often provided as once-in-a-lifetime opportunity. Mountain sheep populations have increased, thanks to partnerships between state and federal governments, and efforts by non-government organizations that provide funding for translocations, research, habitat restoration, disease control, predator management, educational initiatives, and Tribal Nations.

Book chapter↗

USGS2024

Resource availability and heterogeneity affect space use and resource selection of a feral ungulate

Animals adjust their habitat use patterns in response to changes in their physiological needs and environmental conditions. Understanding the mechanisms underlying resource selection and space use across time and space reveals effects of the environment on animals' decisions. We explored the effects of habitat availability and heterogeneity on the seasonal and annual space use and resource selection of two free-roaming feral burro ( Equus asinus ) populations in the United States within distinct climate and habitat conditions: the Sonoran Desert and the Colorado Plateau. As an introduced yet protected species in the United States, understanding burros' interactions with habitat elements is important for their conservation and management, as well as the conservation of sympatric wildlife. We used GPS locations of female burros (72 animals across both study areas) to delineate annual and seasonal ranges and resource selection patterns. We evaluated effects of mean and CV of habitat covariates, including forage, distance to water, and topography, representing availability and heterogeneity of resources, on seasonal and annual range size of burros. Moreover, we explored how burro seasonal and annual resource selection patterns were affected by availability and heterogeneity of resources. In the Sonoran Desert study area, burros had smaller seasonal and annual ranges and constant resource selection patterns across a year, likely due to a freshwater lake in the area, making water a nonlimiting resource. Human presence was the greatest factor affecting range size and resource selection in the Sonoran Desert, where burros selected for areas near roads and human recreation. In the Colorado Plateau study area, where resources were more seasonal, we found larger range sizes and fluctuating resource selection patterns compared to the Sonoran Desert population. Spatial variation in forage, water, and topography significantly affected range size of burros inhabiting the Colorado Plateau study area. Productive habitats with available water support smaller ranges and a more consistent pattern of resource selection. Our results highlight the positive effect of habitat heterogeneity and the negative effect of habitat productivity on range size of animals. Our findings contribute to an improved understanding of habitat requirements for free-roaming burros that currently live under various climate and habitat conditions globally.

Arizona, Utah↗

USGS2024

Rainfall reduces the potential for competitive suppression of a globally endangered ungulate by livestock

Protected areas often are too small to house populations of wide-ranging species. Viability of wildlife populations therefore depends on whether interactions with humans and their land uses are negative, neutral, or positive. In central Iran, we measured interactions between globally endangered onagers (Equus hemionus onager) and livestock by analyzing remotely-sensed vegetation metrics within livestock grazing areas, tracking 9 animals with GPS telemetry, and assessing onagers' diet quality through analysis of fecal samples. Resource selection by onagers depended both on season and the presence of livestock. During the dry season, livestock reduced forage (some combination of forage biomass and forage quality) compared to pre-grazing periods, demonstrating potential for competitive suppression of onagers by livestock when resources are scarce. Additionally, and during both seasons, selection for forage by onagers was accentuated at night when livestock were absent, indicating onager avoidance of livestock. During the wet season, onagers exposed to livestock exhibited higher-quality diets than those that did not co-occur with livestock, suggesting that livestock grazing may potentially enhance forage quality for onagers. Consequently, collaboration with pastoralists to regularly rotate the locations of dry and wet season leases could alleviate negative effects of livestock grazing on onagers. Similar to other cases in multi-use landscapes, temporal shifts in the strength of competition—driven by diel cycles and seasonal rainfall—may characterize wildlife-livestock interactions in Iran and elsewhere in Asian rangelands. Our study highlights the possibility that conservation of an endangered mammal could be compatible with livestock production, at least during wet seasons.

Bahram-e-Goor Protected Area (BPA), Qatrouiyeh Nat↗

USGS2023

Browsers or Grazers? New insights into feral burro diet using a non-invasive sampling and plant DNA metabarcoding approach

By selecting certain plants for consumption, ungulates (hoofed mammals) shape ecosystems and influence which plant species are present in their habitats. We investigated the summer diets of non-native feral burros in two ecosystems: a subtropical Sonoran Desert in Arizona and a temperate juniper shrubland in Utah, the United States. In June and July of 2019, we gathered 50 fecal samples from both locations and analyzed plant DNA in the samples to identify which plants the burros were eating. Our findings revealed that during our summer sampling period, the burros in the Sonoran Desert predominantly consumed woody browse, whereas the burros in the juniper woodland consumed a wide range of flowering herbaceous plants (forbs) and grasses. The burros in the temperate system had to consume a more diverse diet to meet their nutritional needs, while the burros in the Sonoran Desert could rely on two major forage species, mesquite and grasses from the Poaceae family; as a result, their diet had a lower degree of diversity. Feral burros are descended from the African wild ass and exhibit a similar mixed feeding strategy to their ancestors in which they can adapt their diet in different ecosystems to meet their nutritional requirements.

Animals↗

USGS2021

Body size and digestive system shape resource selection by ungulates: A cross-taxa test of the forage maturation hypothesis

The forage maturation hypothesis (FMH) states that energy intake for ungulates is maximised when forage biomass is at intermediate levels. Nevertheless, metabolic allometry and different digestive systems suggest that resource selection should vary across ungulate species. By combining GPS relocations with remotely sensed data on forage characteristics and surface water, we quantified the effect of body size and digestive system in determining movements of 30 populations of hindgut fermenters (equids) and ruminants across biomes. Selection for intermediate forage biomass was negatively related to body size, regardless of digestive system. Selection for proximity to surface water was stronger for equids relative to ruminants, regardless of body size. To be more generalisable, we suggest that the FMH explicitly incorporate contingencies in body size and digestive system, with small-bodied ruminants selecting more strongly for potential energy intake, and hindgut fermenters selecting more strongly for surface water.

Ecology Letters↗

USGS2021

Causes, consequences, and conservation of ungulate migration

Our understanding of ungulate migration is advancing rapidly due to innovations in modern animal tracking. Herein, we review and synthesize nearly seven decades of work on migration and other long-distance movements of wild ungulates. Although it has long been appreciated that ungulates migrate to enhance access to forage, recent contributions demonstrate that their movements are fine tuned to dynamic landscapes, where forage, snow, and drought change seasonally. Researchers are beginning to understand how ungulates navigate migrations, with the emerging view that animals blend gradient tracking with spatial memory, some of which is socially learned. Although migration often promotes abundant populations—with broad effects on ecosystems—many migrations around the world have been lost or are currently threatened by habitat fragmentation, climate change, and barriers to movement. Fortunately, new efforts that use empirical tracking data to map migrations in detail are facilitating effective conservation measures needed to maintain ungulate migration.

Annual Review of Ecology, Evolution, and Systemati↗