Naturalist Participation Varies Between Arizona Counties

iNaturalist participation is unevenly distributed at the global, national, and local scale. I looked at county-level observations in Arizona to try to identify trends and potential causes of variability in total observations and percent of observations identified.

Introduction

Simple hypotheses for the total number of observations in each county could be that the iNaturalist observations vary proportionally to population (based on number of observers) or based on land area (based on availability of organisms to observe).  Alternately, a hypothesis could be that areas with more species, or areas with more parks and tourist attractions, might attract more attention from iNaturalist users. 

Simple hypotheses for the percent of observations identified could be that this varies with the population of a county, so that larger population counties would be more likely to have more experts able to identify local observations.  Although counties with more people might also have more total observations, so this hypothesis could suggest that the percent of observations identified is either consistent across counties or, if the identifier effect predominates, there could be a greater percent in counties with more people.  Conversely, rural counties with low populations that also have lots of observations from visitors (such as to national parks) might have a lower proportion of observations identified.

I queried the iNaturalist.org website in December, 2025 for total observations and Research Grade (RG) for each Arizona county.  Some taxa, like fish or reptiles, might me more abundant in one part of the state over another, so to ensure consistency, I chose a taxa of species that is relatively evenly distributed across Arizona:  flowering plants (angiosperms).  I also obtained county population and land area from publicly available information on the web.  I then calculated % observations ID’d to RG, total species observed, and total RG species confirmed for each county and averages across all counties.

Results

Arizona has 15 counties that vary by orders of magnitude in size, population, as well as other factors that contribute to iNaturalist participation such as number of national parks and tourists.  The largest county by population is Maricopa county, with more than 4.5 million people, whereas the smallest county has less than 10,000 people.  The largest county by land area is Coconino county, with more than 18,000 square miles, whereas Santa Cruz, the smallest county, only has a little more than 1,000 square miles. 

Figure 1 - Arizona Counties

iNaturalist observations of flowering plants vary from only about 3,000 in Greenlee county, to almost 300,000 in Pima county.  RG observations vary from less than 2,000 in Greenlee county, to more than 200,000 in Pima county, with corresponding proportions of observations identified ranging from a low of 46% in Navajo county to a high of 74% in La Paz county. 

Counties vary in documented biodiversity from a high of almost 1,900 species in Pima county, to a low of about 430 species in La Paz county. 

AZ Counties	angiosperm observations	RG angiosperm	% ID'd	species count	RG species	% RG species
Pima	298,000	211,000	71%	2,396	1,855	77%
Coconino	134,440	61,500	46%	2,197	1,489	68%
Cochise	122,500	79,550	65%	1,860	1,460	78%
Yavapai	87,000	48,620	56%	1,798	1,326	74%
Santa Cruz	47,000	28,000	60%	1,586	1,273	80%
Maricopa	217,000	156,000	72%	1,800	1,200	67%
Pinal	41,000	29,000	71%	1,288	976	76%
Gila	26,233	15,500	59%	1,240	938	76%
Mohave	36,000	26,000	72%	1,200	890	74%
Apache	20,468	9,575	47%	1,182	832	70%
Graham	12,700	7,780	61%	1,044	774	74%
Navajo	14,000	6,400	46%	1,000	714	71%
Yuma	18,800	13,800	73%	682	521	76%
Greenlee	3,300	1,895	57%	617	432	70%
La Paz	8,110	6,000	74%	517	429	83%
Average	72,437	46,708	62%	1,360	1,007	74%
Total	1,086,551	700,620		20,407	15,109

Table 1 Arizona Counties Angiosperm plant observations and % Identified

To investigate trends across counties I used Tableau Public to create graphs of total observations versus county land area and population.  Because Maricopa county has 3.5 million more people than the next largest county, I excluded it from the analysis as an outlier. 

While there is a trend toward more observations in larger geographic areas, it is not very strong; the county with the greatest number of observations is right in the middle of the distribution of sizes.  The trend toward more observations with more people is a bit better, but it is dominated by the 2^nd most populated county in Arizona, Pima county.  Removing that county from the analysis essentially eliminates the trend, as the next largest county by population (Pinal) is below the average.

 

Figure 2 Observations by Land Area and Population, excluding Maricopa county.

I then looked at whether the activity of identifies varies with land area or population, and again I did not find simple trends that explain the variation.  It does appear that counties with smaller areas are more likely to have a greater proportion of reported species and observations identified.  This could be explained by the greater tractability of small areas, where large counties have more possible habitats, more potential species, and thus pose greater difficulty to botanists to identify plants across the whole county.  While the largest county, Coconino, does have the largest number of species reported, the smallest county (Santa Cruz) has more than the average number of species reported.  Also, two counties that are in the middle of the distribution (Yavapai and Cochise), have some of the highest number of reported species. 

Figure 3 RG Observations %R by Land Area and Population, excluding Maricopa county.

The trend between population and proportion of identified species is even weaker, with almost no trend apparent.  This leads me to reject the hypothesis that more people in an area necessarily lead to more identifications.

Instead, my current hypothesis, is that observation count is driven by other factors outside of total population or land area.  For example, I think that tourists who visit natural wonders such as the Grand Canyon disproportionately increase the number of observations and species in Coconino county, which results in a corresponding decrease in the proportion of observations and species identified.  In contrast, a county that has a strong resident population of people interested in nature, such as Pima county (Tucson), has a large  number of observations and species, but also has  a large proportion of those observations identified to species.

 

 

 

 

"Average" Rainfall in Arizona

 NOAA National Water Prediction Service reports daily, weekly, monthly, seasonal, and yearly accumulated precipitation and the totals can compared to "normal".  Their data access website states that normal precipitation is defined as the 30-year PRISM normal from 1981-2010.  The Parameter-elevation Regressions on Independent Slopes Model (PRISM) climate mapping system developed at Oregon State University are considered the most detailed, highest-equality spatial climate datasets currently available.

But is the average still the same in the 16 years since 2010?

Methods

I downloaded total accumulated precipitation for water years ending September 30 for the last 10 years.  Unfortunately, the files for many of the years were corrupted and I was only able to look at the three years from October 2022-Oct 2025.  

I clipped the rasters to the Southwest US and took the mean for each grid cell.

Results

Over the last three years, some areas of the Southwest have had 50% of normal precipitation, and other areas have had 150% of normal. 

NOAA NWPS % of normal 2023-2025

Color key:

Zooming in to the area around Prescott, Arizona:

NOAA NWPS % of normal 2023-2025

Conclusions

Most of the area around Prescott is between 85-95% of normal (medium orange), confirming the presence of long-term drought.  Areas less than 75% of normal (dark orange/red) include much of the Bradshaw mountains around Prescott, the Dugas area along I-17, the Mogollon Rim - east of Payson and from Sedona to Ash Fork, and the south slopes of the San Francisco mountains around Flagstaff.

However, there are significant areas between 115 and 125% of normal (light green), including some areas above 125% of normal (dark green).  These above-average areas include the Juniper mountains and Upper Verde River, the Santa Maria river near I-93, a bit of Sedona and Schnebly Hill to Mormon Lake, and the north side of the San Francisco mountains. 

This shows how spatially heterogeneous average rainfall can be, and how a simple description of a state as being in drought or not can be misleading. For example, the excellent Drought Aware web app from Esri shows broad swaths of Arizona currently in drought, but my analysis shows that there is likely much more spatial variability.  

My Attempt to Map a Historic Itinerary

Historic newspapers can be illuminating but also frustrating.  A case in point is the series of articles in the 1864 Arizona Miner detailing "Woolsey's Expedition" in March and April of that year.  

I hoped to deduce some of the actual places visited by the expedition, but the details given were confusing, contradictory, and ultimately insufficient to definitively map where the events took place.  I wonder how many modern newspaper stories, when subject to the same analysis, would fall short?

I analyzed Henry Clifton's account from the May 11, 1864 issue.  The first step was to break the narrative into a numbered itinerary.  I underlined what I thought would be helpful clues, and bolded descriptions I thought would be interesting to compare against present day conditions:

My next step was to try to map the itinerary points on a modern day map.  I added two additionally pieces of information to the text.  First, I looked up that sunrise and sunset were at 6:20am and 6:50pm, respectively. This helps fill in the times for each stop.  Then I filled in the mileage between each stop.  In the table that follows, question marks indicate uncertainty.  The start and stop points correspond to the itinerary above.

In some cases Clifton gives the mileage, and in some cases the stops can be determined so the mileage can be measured, but in many cases he does not give the mileage.  However, based on the travel and rest times I tried to estimate the mileage.  This can also be constrained by the possible stop locations.  For example, when they stop at a creek or a canyon, there are only so many choices for where that could be.  

This map shows their possible itinerary from Woolsey's ranch to the Apache Rancheria on "Squaw Creek".  Tent icons are campsites and hiking figures are other stops.  

Overview map showing likely itinerary points.

Waypoint #4 makes sense if they followed the drainage downstream from "Cottonwood Spring" SE to the next main drainage that could be described as "east fork of the Aqua Fria".  This fork is now known as Ash Creek.  The "Ash Creek" they named at stop #5 is most likely the next major creek to the SE, which is now known as Little Ash Creek.

My best guesses for stop #4 and stop #5.

Many mysteries remain.  First, they claim to do a lot of hiking at night, but this is extremely rough terrain that would be difficult to navigate by night.  According to the US Naval Observatory historical moon phase calculator, this expedition occurred during the waning last quarter of the moon, so they would not have had much light from the moon.  I don't know what kind of lanterns they had, but they don't describe much difficulty traveling at night, other than a description that they had to "descend carefully" to a creek for stop #7.

At stop #6, which occurred sometime after 10 PM on the night of March 31st, Clifton reports finding species of the garlic family on a ridge.  These small plants seem like they would have been difficult to notice by lantern light.  Interestingly, there are only two species of garlic/onions that grow in this area in the spring now.  One, is Crowpoison, which as the name suggests is toxic.  The other is Largeflower onion, which is not common.  

Second, was the Apache Rancheria at modern Squaw Creek or some other location?  It would make sense that their place name stuck, but Squaw Creek is not exactly a unique name so it is possible that other locations have the same name.  Interestingly these creeks that form the southeast boundary of Perry Mesa have been recently renamed Ledni Lii Creek, Gosga Creek, Liya Draw, Che Yagoodiguhn Creek, etc.  I can't find any information about when they were renamed or what the new names mean.

Based on their travel that night from 10 PM until 9 AM and their progress on other legs of the journey, I estimated that they traveled about 10 miles to get there.  However, (for reasons discussed below) I think the site of the Rancheria must have been just upstream of the confluence of Gosga creek and Ilya Draw (AKA North Squaw Creek and Squaw Creek), and this would put them less than 7 miles from camp.  After attacking the Rancheria they managed to get back to camp in less time, so it is possible that they were less than 10 miles from camp.   

Possible site of the Ranchera, upstream of the confluence of Gosga creek and Ilya Draw (AKA North Squaw Creek and Squaw Creek)

In the description of the battle, Clifton states that Company C was west of Company B.  Company B "was in the canon below the rancheria" and chased the Indians up the canyon to where company C was.  Since almost all of the canyons in this part of Arizona run from NE to SW, I had a lot of trouble finding a location where "up canyon" was some westerly.  

Conclusion

Through this exercise of interpreting and attempting to map a historical itinerary, I've come to realize the difficulty of matching newspaper accounts to specific locations.  Without an extremely explicit travelogue, creating a location-based itinerary is either impossible or unreliable.  There were several times when I was ready to give up, but through persevering, rereading the account, and staring at the map I've at least been able to convince myself that some of these locations are approximately correct.  I hope to visit some of these areas in the coming months to retrace the route and add additional information.  

Notes

Note: #PrescottAZHistory blog has an account of Woolsey's expedition that is more of a summary and less of a GIS analysis.  

Note 2: Woolsey organized several expeditions, including a second one in June of 1864 that traversed a much larger area.

Wildlife Trends in Arizona: 150 Years of Winner and Losers

 Arizona’s wildlife history is an example of a timeline that occurred in many developing landscapes: an era of exploitation and eradication (1800s–1950s) followed by an era of restoration and management (1980s–present). 

However, there are some factors that were unique to the United States that led to distinct trends in wildlife populations when compared to those same species across the border in Mexico.

The following summary of research (Part 1) lists 16 Arizona species that were extirpated or greatly reduced and whether they have recovered.  Part 2 looks at 10 species that occur in both Arizona and Mexico and why their populations followed different trends.

This research illuminates the current state of wildlife and ecosystems in Arizona and helps explain the factors that got us here.

Part 1: Arizona vs. Wildlife

The following summary organizes species into groups based on their population trajectories: the “Great Returns” that were extirpated but have been successfully reintroduced, the “Survivors” that have been greatly reduced but still persist, and the “Lost Causes” that were extirpated but have not been successfully reintroduced. 

I. The "Great Returns": Extirpated & Successfully Reintroduced

These species were completely removed from the state but have been restored, often using proxy subspecies or captive breeding.

Rocky Mtn Elk

Extirpation Date/Cause: 1900: The native Merriam’s subspecies was hunted to extinction for meat and teeth.

Reintroduction Date/Area: 1913–1928: Rocky Mtn elk from Yellowstone were released near Winslow, Alpine, & Kingman.

Key Trend/Notes: Ecological Substitution: A proxy subspecies filled the empty niche, expanding rapidly due to lack of competition.

Mexican Gray Wolf

Extirpation Date/Cause: 1970: Eradicated by federal predator control programs (poison/traps) to protect livestock.

Reintroduction Date/Area: 1998: Captive-bred wolves released in the Blue Range Primitive Area.

Key Trend/Notes: Predator Tolerance: Success is biologically high but socially controversial; relies on ongoing conflict management.

 

California Condor

Extirpation Date/Cause: 1924: Vanished due to lead poisoning (bullets in carrion) and shooting.

Reintroduction Date/Area: 1996: Released at Vermilion Cliffs.

Key Trend/Notes: Intensive Care: Survival relies on active management (chelation therapy for lead) rather than self-sufficiency.

River Otter

Extirpation Date/Cause: 1950s: The native Sonora subspecies was  trapped out for fur.

Reintroduction Date/Area: 1981–1983:  Louisiana subspecies released in the Verde River.

Key Trend/Notes: Another Proxy: Like the elk, a non-native subspecies was used to successfully fill the vacant ecological role.

Black-footed Ferret

Extirpation Date/Cause: 1960s: Poisoning of their food source (prairie dogs) led to total extirpation.

Reintroduction Date/Area: 1996: Reintroduced in Aubrey Valley (Seligman).

Key Trend/Notes: Disease Barrier: Success is limited by sylvatic plague; requires dusting burrows and vaccines to persist.

Apache Trout

Extirpation Date/Cause: Mid-1900s: Hybridization with non-native rainbow trout and habitat loss.

Reintroduction Date/Area: 1955–Present: White Mtns (managed by White Mountain Apache Tribe & AZGFD).

Key Trend/Notes: The First Win: Became the first sportfish in history to be delisted from the Endangered Species Act (2024).

 

II. The "Survivors": Reduced but Persisted

These species were decimated by unregulated market hunting or predator control but survived in rugged refugia (escape terrain).

Desert Bighorn

Historic Low Point: Early 1900s: Reduced by diseases from domestic sheep and market hunting.

Survival Factor: Terrain: Survived in the most inaccessible desert peaks (Grand Canyon, Kofa).

Current Status: Translocated: Populations are moved to historic ranges (e.g., Santa Catalinas, Virgin River) to ensure genetic diversity.

 

Mountain Lion

Historic Low Point: 1960s: Bountied as "vermin" until 1970.

Survival Factor: Elusiveness: Solitary nature and rough terrain made total eradication impossible.

Current Status: Stable: Managed as a big game species; populations are robust statewide.

Beaver

Historic Low Point: 1890s: Trapped out of major rivers (San Pedro, Santa Cruz).

Survival Factor: Cryptic Behavior: Survived in deep canyons (Verde/Black River) by using bank burrows instead of lodges.

Current Status: Recovering: Reintroduced to the San Pedro (1999); used today for watershed restoration.

Pronghorn

Historic Low Point: 1920s: Fences cut off migration; market hunting reduced herds.

Survival Factor: Open Space: Remnant herds survived in vast private ranchlands (Babbitt Ranches).

Current Status: Managed: Sensitive to habitat fragmentation; relies on modifying fences for movement.

Gunnison’s Prairie Dog

Historic Low Point: 1930s: Poisoned across vast areas.

Survival Factor: Remote Refugia: Survived in the high-elevation Aubrey Valley; resistant to plague.

Current Status: Keystone: Their persistence allowed the Black-footed Ferret reintroduction to happen.

 

III. The "Lost Causes": Extirpated & Failed (or Struggling) Reintroductions

Complex social behaviors or specific habitat needs made simple reintroduction impossible.

Thick-billed Parrot

Extirpation Cause: 1938: Shooting/Poaching.

Reintroduction Outcome: Failed (1986–93): Chiricahua Mtns.

Why It Failed: Cultural Knowledge: Captive birds lacked flock wisdom to avoid hawks and find food.

Masked Bobwhite Quail

Extirpation Cause: 1900: Cattle overgrazing destroyed tallgrass cover.

Reintroduction Outcome: Struggling (1937–Present): Buenos Aires NWR.

Why It Failed: Habitat Specificity: Reintroduced birds often die due to lack of specific cover and predation; almost entirely reliant on captive releases.

Gila Topminnow

Extirpation Cause: 1940s: Invasive Mosquitofish.

Reintroduction Outcome: Mixed/Struggling: Multiple failures in the 80s/90s.

Why It Failed: Invasive Barrier: Cannot survive where aggressive non-native fish are present.

Jaguar

Extirpation Cause: 1963: Killed as predator.

Reintroduction Outcome: Natural Transients Only: No formal reintroduction.

Why It Failed: Political/Social: Only solitary males currently cross from Mexico; no breeding population exists.

Grizzly Bear

Extirpation Cause: 1936: Killed as predator.

Reintroduction Outcome: Permanently Extirpated.

Why It Failed: Social Tolerance: Requires vast, roadless wilderness that no longer exists in AZ; no plans to reintroduce.

 

Unifying Trends in Arizona Wildlife History:

The Predator Paradox:

Predators (wolves, grizzly bears and black bears, jaguars, lions) were targeted by federal policy for eradication to protect livestock.  Only the cryptic/solitary ones (lions, bears in rough terrain) survived. Reintroducing social predators (wolves) has been biologically successful but socially difficult.

The Proxy Solution:

When a native subspecies was completely lost (Merriam's Elk, Sonora Otter), biologists successfully substituted a close relative (Rocky Mtn Elk, Louisiana Otter).  These ecological substitutes often thrived because the niche was wide open and they were generalists.

The Behavioral Barrier:

Reintroductions of intelligent, social animals (Thick-billed Parrot) or habitat specialists (Masked Bobwhite) often fail.  Hard releases (letting animals go) work for generalists like elk but fail for species that require learned behavior or specific micro-habitats.

Part 2: Arizona vs. Mexico

This analysis breaks down Arizona’s extirpated and reduced species by comparing them to their source populations in other U.S. states and their often-distinct fates across the border in Mexico.

The overarching trend reveals a paradox: while the U.S. effectively managed game species (elk, sheep) through public land regulation, Mexico’s private land system (ranchos) inadvertently served as the final lifeboat for nongame species (wolves, prairie dogs, parrots) that were systematically eradicated in the U.S.

Successful Reintroductions: The Game Bias

The species that succeeded in Arizona were often abundant elsewhere in the U.S. but had been wiped out or severely reduced in Mexico.

Rocky Mtn. Elk

Status in Other U.S. States: Thriving: Millions exist across the Rockies (CO, MT, ID).

Status in Mexico: Extirpated / Rare: Native Merriam’s were also lost in Mexico. Small, private herds of Rocky Mtn. elk exist now on high-fence ranches in Coahuila/Sonora.

Accounting for the Difference: Public Land Management: The U.S. model of public land hunting funded the massive translocation efforts. Mexico lacked the public land base or agency funding to replicate this scale of reintroduction.

River Otter

Status in Other U.S. States: Secure: Abundant in the Mississippi Delta and Pacific Northwest.

Status in Mexico: Critical / Extirpated: The native Sonora otter is likely extinct in the Colorado River Delta due to the complete drying of the river before it reaches the sea.

Accounting for the Difference: Water Policy: Arizona’s otters survive in protected flows (Verde/Salt). In Mexico, the water is siphoned off for agriculture before it can support otter habitat.

Mexican Gray Wolf

Status in Other U.S. States: Extirpated: Historically ranged into NM/TX (now reintroduced there).

Status in Mexico: Reintroduced (Struggling): Mexico began releasing wolves in the Sierra Madre in 2011. The population is smaller and more fragile than the AZ/NM population.

Accounting for the Difference: Prey Base: In Arizona, wolves rely on abundant elk. In Mexico, elk are absent and deer are scarcer, forcing wolves to target livestock, leading to immediate conflict with ranchers.

Reduced/Survivors: The Refugia Divide

Species that held on in Arizona often did so in rugged terrain, while in Mexico, their fate depended heavily on the stewardship of individual landowners.

Desert Bighorn

Status in Other U.S. States: Stable: NV, CA, and UT have strong, managed herds.

Status in Mexico: Stable / Commercialized: In Sonora and Baja, bighorn are a high-value commodity. Private ranchers protect them aggressively to sell high dollar hunting tags ($50k+).

Accounting for the Difference: Economic Incentive: In the U.S., bighorn are protected by state agencies as a public trust. In Mexico, they survived because they became a private asset worth protecting from poachers.

Pronghorn

Status in Other U.S. States: Secure: WY and MT have massive herds.

Status in Mexico: Endangered (Sonoran Subspecies): The Sonoran Pronghorn (El Pinacate) is critically endangered.

Accounting for the Difference: Barriers: The U.S. herds had open range. The Mexican herds were hemmed in by highways (Hwy 2) and border fencing, severing their ability to find water during droughts.

Beaver

Status in Other U.S. States: Abundant:  r egained range across the West.

Status in Mexico: Recovering (Delta): The Colorado River Delta saw a miraculous, short-term return of beavers following the "Pulse Flow" (Minute 319) water release in 2014.

Accounting for the Difference: Resilience: Beavers in Mexico proved they are waiting in the wings; they only lack the water, whereas U.S. populations had consistent flows in mountain refugia.

Failed/Struggling: The Mexican Lifeboat

Species that failed in Arizona (often due to poisoning or habitat loss) survived in Mexico, which served as the last stronghold.

Masked Bobwhite

Status in Other U.S. States: Extirpated: Only exists in captivity/refuge.

Status in Mexico: Critical / Persistent: Small wild populations were rediscovered on private ranches in Sonora (e.g., Rancho Carrizo) in the late 20th century.

Accounting for the Difference: Grazing Intensity: While U.S. ranchers switched to exotic grasses (Lovegrass), some remote Sonoran ranches maintained native vegetation due to isolation and traditional (lower intensity) grazing practices.

Thick-billed Parrot

Status in Other U.S. States: Extirpated: No wild flocks in the U.S.

Status in Mexico: Endangered / Extant: ~2,000 birds breed in the Sierra Madre Occidental (Chihuahua/Durango).

Accounting for the Difference: Old Growth Timber: Arizona logged its sky island nesting snags by the 1930s. The remote Sierra Madre retained old-growth forests longer (though these are now threatened by logging).

Jaguar

Status in Other U.S. States: Extirpated: (Breeding populations).

Status in Mexico: Vulnerable / Breeding: A reproducing population exists in Sonora (Northern Jaguar Reserve), only ~120 miles south of the border.

Accounting for the Difference: Road Density: Arizona is crisscrossed by paved roads and development. The Sonoran habitat is more rugged, roadless, and largely privately owned, reducing human-cat interaction.

Black-tailed Prairie Dog

Status in Other U.S. States: Extirpated: Widespread poisoning campaigns.

Status in Mexico: Thriving (Janos): The Janos Biosphere Reserve in Chihuahua holds one of the largest prairie dog complexes in North America.

Accounting for the Difference: Benign Neglect: The U.S. government funded industrial-scale poisoning. The Mexican government lacked the funds for such programs, inadvertently allowing the massive colonies to survive until conservationists bought the land.

Summary of Differences

The Industrial Efficiency of Extirpation

Arizona’s extirpations were often more thorough than Mexico’s because the U.S. had the resources to be efficient. Government-sponsored predator control (wolves/jaguars) and poisoning (prairie dogs) were well-funded industrial operations in Arizona. Mexico, lacking these centralized resources, allowed "pest" species to survive simply through "benign neglect."

Public vs. Private Conservation

Arizona: Success relies on public land management (US Forest Service/BLM). This is great for generalists like elk but hard for specialists that need specific micro-habitats.

Mexico: Survival has relied on private land isolation. Remote ranches in the Sierra Madre acted as unintended nature preserves because they were too difficult to log or develop.

The Elk Gap

The single biggest ecological difference today is elk. Arizona replaced its lost native elk with a massive, successful herd of Rocky Mountain elk. Mexico never did. This means Arizona has a massive prey base for wolves and lions that Mexico lacks, creating a "food imbalance" at the border that complicates predator recovery in the south.