Heartland Ranch the site of another ferret release – this time utilizing GPS-tracking collars developed by Smithsonian’s National Zoo and Conservation Biology Institute scientists

A black-footed ferret wearing one of  new tracking collars is shown after being released November 19 at Heartland Ranch Nature Preserve  (this and all photos in article courtesy of CPW)

Heartland Ranch Nature Preserve, a sprawling 43,000 acre tract of land southwest of Lamar, comprises the largest part of Southern Plains Land Trust’s nearly 63,000 acres – land devoted to protecting and conserving native plants and animals.  Several animals once native to this area have been reintroduced and now roam there freely, including herds of bison, elk, pronghorn and mule deer. Since 2022, Heartland Ranch has been one of several locations chosen as a reintroduction site for the black-footed ferret (Mustela nigripes), the only ferret species native to North America. Prairie dogs make up more than 90% of this ferret’s diet and these prairie dog colonies have seen their numbers decline by an estimated 98% over the past century.  Reasons for this decline include habitat loss from agricultural and urban development, as well as poisoning, shooting and other human intolerances.  Tied directly to this decline was the near-demise of these once-abundant ferrets when their main food source disappeared.

This critically-endangered species was actually thought to be extinct until 1981, when a sheepdog in Wyoming dropped a ferret carcass on its owners doorstep.  Since then, captive breeding programs have been successful, allowing areas like Heartland Ranch the opportunity to harbor these small, elusive creatures in hopes that their numbers will repopulate. Along the way, these captive-born ferrets can fall prey to larger animals including foxes, badgers, coyotes, and eagles. Raised from birth above ground without the fear of predators, these reintroduced ferrets lack some of the “street savvy” their predecessors possessed, making them more vulnerable to predation.  Upon arrival at a relocation site, the ferrets are released into existing prairie dog burrows, where they begin their new life underground and learn to rely on their innate hunting skills to survive.  Heartland Ranch has 33 well-established, thriving prairie dog colonies which are plague-free thanks to efforts by both SPLT and Colorado Parks and Wildlife, who regularly treat the colonies with both flea-killing agents and a plague vaccine hidden in tasty pellets.  This availability of a healthy food source for ferrets made Heartland a perfect choice for the ferret reintroduction program.

Before release, each ferret is tagged with a PIT (passive integrated transponder) tag – a tiny, implantable microchip similar to those used for house pets that helps with identification after release.  The tags transmit a unique identification code to a handheld reader.  Since the released ferrets spend the vast majority of their time underground in the burrows and are nocturnal, monitoring their survival has thus far been limited to nighttime spotlight surveys, in which known burrows are observed overnight by wildlife officials and volunteers who travel among the prairie dog colonies, looking for the unique green reflection of the ferrets’ eyes reflected in their spotlights.  Once spotted, an attempt is made to read the ferret’s tag but once the animal retreats underground, that isn’t always possible due to their speed and the vast underground network of tunnels.  The most recent spotlight survey at Heartland this fall did not result in any ferrets being seen.  While concerning, it wasn’t necessarily indicative of the lack of any live ferrets at the preserve – it only means that on that particular night they didn’t show themselves to the observers.

A black-footed ferret is fitted with GPS-enabled collar prior to its release at Heartland Ranch

Development of new cutting-edge technology by the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) hopes to improve on the ability to detect the ferrets.  A first-ever tracking study is being conducted at Heartland Ranch following  the November 19 release of 20 new ferrets from the Wellington breeding site fitted with the novel collars developed by NZCBI.  The collars utilize GPS/satellite technology to collect data. Information from the NZCBI website about the program quotes Jesse Boulerice, a research ecologist there, as saying “We have never been able to collect this type of information on black-footed ferrets. This technology holds immense potential to help us understand the drivers of survival and mortality of these mysterious creatures, as well as increase our knowledge about their movement, behavior, and activity patterns.  We simply don’t know enough about what is happening underground where ferrets spend most of their time.  This data is expected to be critical for informing future reintroduction and conservation strategies”.   Colorado Parks and Wildlife officials are working in conjunction with the Smithsonian biologists in this study at Heartland.

Another of the newly-collared ferrets awaiting release onto Heartland Ranch

These newly-released ferrets are being tracked by sophisticated drones, allowing biologists the ability to visualize the complex three-dimensional structure of the burrow systems which can provide a detailed understanding of how these animals move and behave within those underground ecosystems.  The window for drone-spotting of the ferrets will be very short, likely 7-10 days, as the collars are frequently rubbed off due to the tunneling actions of the animals as well as their tubular body shape.  This study is ground-breaking in its opportunity for researchers to identify any cause-specific mortalities – research not attempted in the last 30 years. “This project aims to enhance our understanding of the relationship between black-footed ferrets and their predators” said Jonathan Reitz, CPW Wildlife Biologist.  “Specifically, we are investigating which species prey on any black-footed ferrets in the two weeks following the ferret release”.

A drone being used to monitor the ferrets wearing the GPS collars after release

An unfortunate result of CPW’s press release concerning this upcoming study and the results of the most recent spotlight survey at Heartland was the proliferation of news outlets making assumptions and statements in articles, such as one made by a Colorado Sun reporter who said “biologists’ most recent fall survey found zero evidence that any (of the 100 ferrets released at Heartland since 2022) had survived”. Having previously done research about the ferret program at Heartland for a story published in The Prowers Journal, I knew how elusive these ferrets were to monitoring efforts, so I reached out to Drs. Henry Pollock and Judith Westveer, who are the Executive Director and Associate Director, respectively, of Southern Plains Land Trust to get more insight into the situation. Pollock and Westveer have been an integral part of the ferret reintroduction project at Heartland since its inception.

Speaking to me about the more than 100 ferrets who have been released on the property since 2022, Dr. Westveer said “Let me clarify something about the ferrets on SPLT; we actually did see survival in the previously introduced ferret groups last year. Even a year after reintroduction, they were still spotted on Heartland Ranch, which makes us optimistic about them reproducing in the wild.  This year they have been a little bit trickier to find; however, we are talking about finding a needle in a haystack.  They are nocturnal animals that spend only minutes per night outside of a burrow when they are potentially visible to spot.  They could be anywhere on 43,000 acres.  We had four groups per night in a vehicle, driving up and down prairie dog colonies.  Spotting a ferret is super tricky, so it could be circumstantial that we did not find a ferret this year.  Full moons tend to keep nocturnal animals out of sight and if there is any noise from the observers, they won’t come out of the burrow.  We had people at the prairie dog burrows a couple of weeks before this survey was conducted to do the annual plague prevention treatment, which could have made them shy, etc.  It’s not correct to immediately state that they are all dead, as the article in the Colorado Sun suggested”.  She continued “However, there is good news: this year we have put tracking collars on several newly introduced ferrets to see where they go and if they encounter any badgers or swift foxes. This will help us to better understand what challenges they might face after release and if so, we can make their reintroduction even more successful in the future”.

Westveer also wanted to mention that SPLT has the best plague mitigation program in the country among all prairie dog sites, saying “our acres have grown steadily at 20-30% each year, from 500 prairie dog acres in 2015 to 3,200 as of the beginning of 2025.  Ferrets are an important emblem of the prairie dog ecosystem that helps to raise awareness and support for prairie dogs, which are more controversial and which people are less likely to support.  The reality is that nobody knows whether the ferrets are alive or dead because (until now) it has been impossible to track them – which is where we come in.  This is really a one-of-a-kind study where we track ferrets and their predators, to make sure they get a better chance of survival in the future” she said.

Dr. Pollock reiterated this, adding that the new technology the ferret collars provide will allow the researchers to not only track the animals in real time, but also to ascertain what predators may have been involved in the recent lack of visualization during the fall spotlight survey.  He said that the preserve currently monitors twenty badgers wearing GPS collars as well as twenty swift foxes who are equipped with GPS backpacks and this data, overlapped upon the tracking information the ferrets will contribute, can help them ascertain what future steps might need to be taken to ensure the survival of ferrets at Heartland.  These steps could include fencing or even translocation of predators to other areas on the property if necessary. If data collected by the drone tracking does show no live ferrets, it should provide researchers with answers as to why this is occurring once the discarded collars have been retrieved and the data contained in them analyzed. Although no dead ferrets have been found at Heartland at any time since the first release in 2022, Pollock told me that if in the future they are, DNA testing is available that could help identify the predators through such methods as saliva samples.  Since this is the first time the addition of the high-tech collars has been used, he said “no one really knows what to expect” as far as any data the collars may provide but is excited about the program and its potential.  He wanted to express thanks to not only the Smithsonian for its groundbreaking work but also to Fish and Wildlife, National Resources Conservation Service, and Colorado Parks and Wildlife who, he said, “is our biggest partner” in efforts to repopulate and maintain Heartland Ranch and its many native species.  He also wanted to recognize the ranchers and landowners who allow the ferrets to be released on their properties as part of the huge effort towards the repopulation of the species. The ultimate goal of the ferret reintroduction program is for the species to thrive and reproduce in the wild.  This natural reproduction has recently been evidenced at the May ranch north of Lamar, another local reintroduction site, where young (untagged) kits have been spotted.  Pollock told me “there is a higher predator load” at Heartland than at the May’s ranch which could be a factor in those births, but he is optimistic that this reproduction can occur at Heartland as well.

Drs. Pollock and Westveer promised to keep me informed of any data gleaned from this new study when it is available, as well any new information regarding the ferrets at the preserve.   More information about SPLT and the ferret releases on their property can be found at their website: https://southernplains.org

By: Barbara Crimond