HERD SOCIAL STRUCTURES
ISPMB herds show that functional social structures contribute to low herd growth compared to BLM managed herds

September 2013

 

As we complete our thirteenth year in studying the White Sands and Gila herds, two isolated herds, which live in similar habitat but represent two different horse cultures, have demonstrated much lower reproductive rates than BLM managed herds.  Maintaining the “herd integrity” with a hands off management strategy (“minimal feasible management”) and no removals in 13 years has shown us that functional herds demonstrating strong social bonds and leadership of elder animals is key to the behavioral management of population growth.


ISPMB’s president, Karen Sussman, who has monitored and studied ISPMB’s four wild herds all these years explains, “We would ascertain from our data that due to BLM’s constant roundups causing the continual disruption of the very intricate social structures of the harem bands has allowed younger stallions to take over losing the mentorship of the older wiser stallions.


In simplistic terms Sussman makes the analogy that over time Harvard professors (elder wiser stallions) have been replaced by errant teenagers (younger bachelor stallions).  We know that generally teenagers do not make good parents because they are children themselves.


Sussman’s observations of her two stable herds show that there is tremendous respect commanded amongst the harems.  Bachelor stallions learn that respect from their natal harems.  Bachelors usually don’t take their own harems until they are ten years of age.  Sussman has observed that stallions mature emotionally at much slower rates than mares and at age ten they appear ready to assume the awesome responsibility of becoming a harem stallion. 


Also observed in these herds is the length of time that fillies remain with their natal bands.  The fillies leave when they are bred by an outside stallion at the age of four or five years.  Often as first time mothers, they do quite well with their foals but foal mortality is higher than with seasoned mothers.


Sussman has also observed in her Gila herd where the harems work together for the good of the entire herd.  “Seeing this cooperative effort is quite exciting,” states Sussman. 


ISPMB’s third herd, the Catnips, coming from the Sheldon Wildlife Range where efforts are underway to eliminate all horses on the refuge, demonstrate exactly the reverse of the organization’s two stable herds.  The first year of their arrival (2004) their fertility rates were 30% the following first and second years. They have loose band formations and some mares are without any harem stallions.  Stallions are observed breeding fillies as young as one year of age.  Foal mortality is very high in this herd.  Generally there is a lack of leadership and wisdom noted in the stallions as most of them were not older than ten years of age when they arrived.  In 2007, a decision to use PZP on this herd, a contraceptive, was employed by ISPMB.  This herd remains a very interesting herd to study over time according to Sussman.   “The question is, can a dysfunctional herd become functional,” says Sussman who speculates that the Catnips emulate many of the public lands herds.


In 1992 when Sussman and her colleague, Mary Ann Simonds, served on the National Wild Horse and Burro Advisory Board, they believed that BLM’s management should change and recommended that selective removals should begin by turning back all the older and wiser animals to retain the herd wisdom.  Sussman realizes that the missing ingredient was to stop the destruction of the harem bands caused by helicopter roundups where stallions are separated from their mares.  “Instead, bait and water trapping, band by band, needed to be instituted immediately,” says Sussman.  Had this been done for the past twenty years, we would have functionally healthy horses who have stable reproductive rates and we wouldn’t have had 52,000 wild horses in holding pastures today.   BLM’s selective removal policy was to return all horses over the age of five.  When the stallions and mares were released back to their herd management areas by the BLM, younger stallions under the age of ten fought for the mares and took mares from the older wiser stallions.  This occurs when there is chaos happening in a herd such as roundups cause. 


Sussman also believes that when roundups happen often the younger stallions aged 6-9 are ones that evade capture.  This again contributes to younger stallions taking the place of older wiser stallions that remain with their mares and do not evade capture.  She is advocating that the BLM carry out two studies: determining the age of fillies who are pregnant and determining age structures of stallions after removals.

 

Currently Sussman is developing criteria to determine whether bands are behaviorally healthy or not.  This could be instituted easily in observation of public lands horses.


Taken from BLM’s website:  “Because of federal protection and a lack of natural predators, wild horse and burro herds can double in size about every four years.”   


White Sands Herd Growth1999-2013 – 165 animals. 

BLM’s assertion herds double every four years means there should be 980 horses or more than five times the growth of ISPMB’s White Sands herd.


Gila Herd Growth: 1999-2013- 100 animals 

BLM’s assertion herds double every four years means there should be 434 horses or nearly four times the growth of ISPMB’s Gila herd. 


Sussman says that BLM’s assertion as to why horse herds double every four years is incorrect. The two reasons given are federal protection of wild horse herds and lack of natural predators. ISPMB herds are also protected and also have no natural predators, but they do not reproduce exponentially. She adds that exponential wild horse population growth on BLM lands must have another cause, and the most likely cause is lack of management and understanding of wild horses as wildlife species.  Instead BLM manages horses like livestock. “According to the Wild Horse and Burro Act of 1971, all management of wild horse populations was to be at the ‘minimal feasible level’,” Sussman says. “When the BLM’s heavy-handed disruption and destruction of wild horse social structures is the chief contributing factor in creating population growth five times greater than normal, than the BLM interference can hardly be at a ‘minimal feasible level.’” 


Sussman concludes that ISPMB herds are given the greatest opportunity for survival, compared to the BLM’s herds which are not monitored throughout the year.  “One would assume,” Sussman says, “herds that are well taken care of and monitored closely would have a greater survival rate.  Yet, even under the optimum conditions of ISPMB herds, they still did not increase nearly 500% like BLM herds.”   


Karen Sussman has been riding horses since the age of four.  She has spent the last thirty-two years working with wild horses and burros and has been involved in every aspect of the BLM’s Wild Horse and Burro program including: assisting in the development of a consistent training program for the prison training program, development of a volunteer compliance program for adopted wild horses and burros, a catalyst for the increasing fines from $2,000 to $100,000 for the death of wild horses or burros, monitoring fee-waivered animals in Montana.  Sussman received the prestigious Health of the Land Award serving on the BLM’s Black Mountain Eco-team developing a gold-standard model for managing wild burros.  She served on the National Wild Horse and Advisory Board in 1990-92.


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