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A Southern California Struggle: Mountain Lions and the Effects of Human Encroachment

The walls are closing in one of our most important predators in the United States. Getting pushed to find refuge in their shrinking home by escaping to the furthest corners they can reach. Mountain lions (Puma concolor) are struggling to find a place amongst a species who has lost sight of their role within the natural world. Humans are one of the deadliest forces for these wild species in modern day society. Only to inflame our continual drive to build in the name of “progress”, leading to detrimental effects on the wild places that provide so much for our lives.  Creeping our way through untouched landscape and finding a way to take up arms against wildlife as they try to adjust. What can we expect to see from this type of change? What have we already been coping with?


            Human encroachment is leading to the loss of habitat available for our wild neighbors to create suitable home ranges and survive. We look to build homes in the spacious and beautiful places that were only considered this way due to the fact they were untouched. However, we now flock there with our homes and vacation properties that soon cause further development to follow. All of these scars on the land are pushing wildlife to disperse important habitats for their survival, but there is only so far they can go when we keep closing in. Looking at the numbers, we can see that there is a growing issue throughout the world. In the United States alone, our population has increased by 26.2 million people from 2010 to present (U.S. Census Bureau quickfacts: United States). The influx of humans on the landscape means that we need to create places for these people to live. Looking in my own backyard, the figures are startling. From 2001 to 2021 landscape data from the Multi-Resolution Landscape Characteristics Consortium shows a troubling trend of losing natural lands here in San Diego County. Over the last 20 years we have seen a 5.54% increase in total developed areas, a 9.05% increase in impervious surface area, and a 41.69% decrease in forested areas (MRLC NLCD Eva Tool). These staggering numbers are the reason you may be hearing about what is known as habitat fragmentation. A phenomenon that is being caused by over-development and has negative consequences for the wildlife fighting for survival in a human dominated world.

            To understand the full effects that altering the health of mountain lions can do to the ecosystems they reside in, we must first understand the roles they play there. As a keystone species, the mountain lion can regulate populations of other species that left unchecked can lead to disruption to the landscape. Prey species like the mule deer (Odocoileus hemionus) are herbivores and graze on different plants throughout their range. If mule deer were to lose this top predator, there could be huge consequences to the abundance of their forage species and further effects reaching throughout the environmental community (categories of keystone species, see Appendix I). These connected consequences are known as a trophic cascade and can cause entire ecosystems to disappear. A good example of this happening is with grey wolves (Canis lupus) in the Greater Yellowstone Area. By the 1920’s there were no wolves left in Yellowstone after the immense hunting pressures of a bounty system was set for predator control (Beschta and Ripple, 2021). Getting rid of the wolves was the end goal here and mountain lions came under fire as well, although the more secretive behavior of the large felid was able to sustain more of the onslaught from the bounty. However, the lack of understanding that we had about natural processes lead to adverse effects for all life in the region. As the wolf’s primary prey, the elk (Cervus canadensis), went unregulated from their biggest predator and took over the landscape there was irreversible damage done to the park from trampling and over grazing that can still be seen in Yellowstone today (Beschta and Ripple, 2021). These issues can be repeated in any ecosystem when a keystone species is removed, making it is so important to focus on them and make sure that we are protecting their habitats.


            Unfortunately, we are struggling to protect these important home ranges for the keystone species we all rely on. Many factors for this shortcoming are at play and cause more stress on everything living within the region. Whether it is outdated management techniques, lack of funding, or even the lack of support from a political standpoint. All these factors and more are contributing to an ongoing and increasingly stressful environment for the mountain lion to continue to survive in. The main course of action that humans take to interfere with the natural state of wildlife is to develop their habitats. The population boom and need for more infrastructure to support this growth has lead to greater landscape changes across the natural range of the mountain lion. In California the land is being parceled out in portions ranging from 1-40 acres at a time (Human/Wildlife Interactions in California: Mountain Lion Depredation, Public Safety, and Animal Welfare - Amendment to Department Bulletin 2013-02). As these areas of developed lands grow and start connecting with other parcels it causes habitat fragmentation.


            Learning the behaviors of different species and what they need in a habitat to sustain healthy populations gives us deeper insight into the full extent of consequences habitat fragmentation has on them. Individuals of a cougar population can be grouped into four categories; adult males, adult females, dependent young, subadults or transients (Negri et al. CH. 5 Cougar Population Dynamics). Male mountain lions are known to have larger home ranges than that of females. Males will establish a territory that encompasses the same area as multiple females’ home ranges to secure his reproductive success in the area (Negri et al. CH. 5 Cougar Population Dynamics). Males are also territorial by nature and will defend their home range aggressively from other male competitors or young that were not sired by him. This territoriality is believed to play a role in the natural regulation of populations, but when mixed with humans disturbing the land, there are other issues that arise with these population dynamics. Habitat loss and fragmentation are one of the greatest risks to mountain lions and many other species on our landscapes.

It comes when large areas of suitable habitat are divided and developed for various reasons such as industrial, residential, roadways, and more. By adding these aspects to the landscape there are processes being interrupted that affect mountain lions in intricate ways. Intraspecific killings, where one species will kill another individual of the same species, is a major component to the mortality rate of this species. Because the fragmentation of land is cutting them off from obtaining their own independent ranges in other habitats, it worsens the issue of mountain lions killing mountain lions (Lions in the Santa Monica Mountains). Additionally, we are also causing increased risk of mortality to mountain lions from road development alone. Habitat fragmentation leads to increased vehicle collision deaths of these large felids due to the expanding maze of highways (Lions in the Santa Monica Mountains).  The dangers here are not only to the mountain lion, but every single individual who gets behind the wheel and travels these highways. A collision with one of these animals could be deadly to both parties and other motorists on the highway. It could also be avoided completely. The use of wildlife crossings allow for these animals to move past our anthropogenic boundaries and reestablish habitat connectivity (Lions in the Santa Monica Mountains).

            Facing the effects of shrinking habitats, it is important for humans as a collective to understand and help implement practices to support mountain lion dispersal. They rely on it to maintain healthy genetic flow, reestablish historic range, and in avoiding intraspecific mortality. Typically, dispersal is witnessed in young subadult males, however, about 50% of female mountain lions will also disperse while the remainder stay philopatric to their natal areas (Hornocker et al. CH. 8: Behavior and Social Organization of a Solitary Carnivore). The act of dispersing from the natal range of a mountain lion comes around 14 to 16 months. As they learn all the necessary skills of survival from their mother, individuals that end up dispersing will set out on a daunting journey. They will have to navigate through territories of older territorial male lions that these young subadults are not equipped to battle and find passage through the sprawl of human development. Roadways, residential communities, and rural farms all pose challenging obstacles for these newly independent cats to avoid. Some of these young mountain lions have been recorded using small transient home ranges as they move, thought to be for prey resources and for avoiding territorial males in the area (Beier 1995; Logan and Sweanor 2001). This is where we can see the importance of maintaining the connectivity of their habitat. The less room they have access to, the deeper they get pushed into a corner they cannot escape.


            Mountain lions need space for many reasons including their large home ranges extending up to 150 square miles, to avoid competition for mates, and secure a sustainable prey resource. They also depend on being able to reach other populations to maintain their genetic diversity. The Florida panther (Puma concolor coryi) is a subspecies of Puma concolor, the mountain lion, and is one of the most endangered large mammals in the world (Florida panther - army). The cause of this was the product of habitat fragmentation. A once connected population from western Louisiana all the way to eastern Florida and potentially further north, was cut off and began to dwindle in numbers. The inbreeding caused by geographic isolation and habitat loss lead to the loss of their genetic variability (Florida panther - army). Showing us the importance of supporting a natural and suitable habitat for the mountain lion. As we continue to divide the land into more sections of altered landscape across the entire range of this species, it is likely for us to see the same damaging effects as the Florida panther occurring in other areas. Humans keep closing in and tightening its grip around the elusive apex predator and the list of consequences reaches even further. Directly affecting those who live in or frequently visit the places mountain lions roam.


More than half of California is suitable mountain lion habitat and   coupled with behavior that is extremely solitary, elusive and has a strong proclivity to avoid humans, the strain of human encroachment becomes more evident. Between the periods of 2007 and 2013 there has been a substantial increase in the amount of wildlife interactions that have taken place in California (Human/Wildlife Interactions in California: Mountain Lion Depredation, Public Safety, and Animal Welfare - Amendment to Department Bulletin 2013-02). This is one of the biggest concerns when looking at the consequences of altering landscapes and adjusting their purpose to fit into our “modern” society. Because we have conducted large scale development, we also encounter the problems that come along with habitat fragmentation. When society clashes with nature we must abandon our perceptions of human reactions. What we define as malice, greed or evil does not exist in the animal kingdom, only survival. It is easy for the rancher to lose a cow to a mountain lion and conclude that if one will do it, they must all do it because they enjoy killing or kill because food is available. This is not the case, and we must dissect the factors that lead to depredation and human-mountain lion conflict to uncover how we can avoid them. Being solitary and elusive creatures, they try to avoid areas of human activity. Though issues can arise when dispersal has been cutoff for mountain lions forcing them to step outside of their known behavioral patterns to survive. One of the issues is depredation, and it has been on the rise in California for many years. From 1 depredation incident in 1972 to 323 in 1995, there is clearly something leading to the increase (Mansfield and Charlton). With direct connections between human activity and depredation incidents the picture becomes clearer as to what could be causing increased conflict. In California, the depredation of domestic sheep correlates to the amount of suitable habitat in a given county, and pet depredations are linked to the average amount of residential development in the state each year (Mansfield and Charlton). Correlations like this shows the true impact that our actions are having and where our future is headed. These components have also lead to the increased human-cougar encounters, furthering the strained relationship between people and mountain lions.


The magnitude of humans encroaching into mountain lion habitat is only exacerbated when humans come in direct contact with them. When a someone is injured by any type of wild predator, it usually has one of two responses. One community will defend the animal and state that when living or exploring wild habitats, you must expect to encounter and potentially have conflict with wildlife. There is another community that condemns the wildlife and call for the reduction of “dangerous” predators. However, there is a connection to reestablishing habitat connectivity and potentially reducing human-mountain lion conflict. The answers may reside in the ability of these large cats to leave the areas they were born into. Young subadult mountain lions dispersing from their natal range are doing so for two reasons. The avoidance of inbreeding and reduction in competition for resources could possibly work together in causing strong selection for males to disperse and females for reasons related to population density (Wrangham & Peterson, 1996). Mountain lions generally choose to disperse through suitable habitat, however, as the landscape is under constant construction, these lions have to travel unsuitable areas as quickly as possible and find habitat patches they can use to escape the urbanized and non-habitat locations along their journey (Hornocker et al., 2010). Because some populations, especially those around metropolitan areas, suffer from loss of dispersal routes they have two options to consider when faced with the imminent task of leaving. Attempt the trek through a foreign landscape, dominated by dangerous thoroughfares and a maze of bizarre structures. This option poses a great risk of death to the mountain lion from human-caused mortality. Their other option is to move away from the dominant male of their natal range and find a quiet corner of the habitat away from the activity of the territorial individuals that pose the most risk. Both stressors could be alleviated with the implementation of management techniques that support the protection of connected habitat and the reestablishment of connectivity to areas where mountain lions have lost their important dispersal routes.

            One of the biggest ways we can make real changes that ensure a connected habitat for the large cats to access is to implement the use of wildlife crossings. By adding these safeguards to ongoing and upcoming projects, we can begin the process of reestablishing habitat connectivity that will benefit all species. Measures that have been effective is the use o fencing along highways with openings at wildlife crossings to guide wildlife to use these safe passages and avoid collisions with vehicles (California wildlife-vehicle conflict report P-22 edition). For mountain lions specifically, this will open the landscape back up to allow better dispersal and helping the genetics of different populations mix. Learning from the extreme consequences of the Florida panther the importance of opening these landscapes back up is becoming more critical. The mountain lion isn’t the only species that benefits from these changes either. Well-connected natural landscapes allow every other species to take advantage of population immigration and emigration, finding home ranges away from territorial individuals within their habitat, finding better food resources, and so many more. For landowners that are situated in prime mountain lion habitat, there are certain things that can be done to help prevent conflicts with the large cats. For those who have pets (dogs, cats, etc.), keeping their food indoors and avoiding letting them outdoors unattended, especially during night, dawn and dusk. For people that have livestock; providing indoor or covered areas for their herds to congregate at night, installing motion activated lights and sound systems, and removing underbrush and thick vegetation in areas where their herds have access to are all ways to decrease the likelihood of depredation incidents. California has a policy in place concerning the procedures involving depredation, not without fault, but I believe to be a great step in the right direction. The process includes three separate phases where lethal measures are a last resort and focus on the education of property owners on better husbandry practices [APPENDIX III (Human/Wildlife Interactions in California: Mountain Lion Depredation, Public Safety, and Animal Welfare - Amendment to Department Bulletin 2013-02 2017)]. With all these factors working in concert there is hope for the overall health of our planet starting with our own backyards. [see also Appendix II: Seven Levels of Conservation Ambition for Large Carnivores (Ray et al., 2013)


Without acting against the core issue of these adverse encounters with mountain lions and a true understanding of what we are putting them through, we are failing not only the large predator, but all species that depend on its regulation of the ecosystem. We are putting more pressure on conservationists to convince people to listen to the science when the fear of public safety is clouding their vision to the facts. Conservation and management of mountain lions is very complex and is highly variable geographically. This makes continued research, resources and efforts directed toward further understanding the best methods for each local population.  I have spoken about how the actions of humans have been boxing mountain lions into a corner, giving the perception our back is clear. As we push the mountain lion further down this destructive path and into its metaphorical corner, we are putting all other species and ourselves in the same predicament. Without accepting we need to learn more,we are putting the health and sustainability of all wildlife at risk and consequently our own.





APPENDIX I: Keystone Species Categories (Denchak, 2019)

a. Predator: keeping population and range of prey in check

i.     Impact other predators as well as other animal and plant species farther down the food chain

ii.     Effects of Removal: population of its prey can explode pushing out other organisms and affecting species’ diversity (known as trophic cascade)

b. Prey: serve as critical food source for predator populations

i.     Less likely than other prey species to become rare or extinct

c. Ecosystem Engineer: create, modify, or maintain the landscape around them

i.     Influence prevalence and activities of other organisms and help define the overall biodiversity of their habitat

d. Mutualist: two or more species that engage in reciprocally vital interactions

i.     Disruption of one species will affect the other and ultimately all species in the ecosystem

ii.     Example: pollinators (bees, hummingbirds) and plants

e. Plants: Provide a critical source of food and/or shelter for other species


Appendix II: Seven Levels of Conservation Ambition for Large Carnivores (Ray et al., 2013)

a.     Species Presence: e.g. Lynx (Lynx lynx) persist in an area following recolonization or reintroduction

b.     Some ecosystems process occur: e.g. the lynx begin to eat roe deer (Capreolus capreolus) (predation), kill red foxes (Vulpes vulpes) (intraguild predation), and leave carcasses for scavengers (secondary effects)

c.     Species demographic viability is achieved: e.g. this lynx population increases to a level of demographic viability

d.     The evolutionary potential of the species to adapt to future conditions is maintained: e.g. the population increases to a level (of size or connectivity with other populations) where genetic viability (evolutionary potential) is ensured

e.     The full community of carnivores (and their prey) is restored: e.g. lynx, wolves (Canis lupus), and bears (Ursus arctos) occur in the same area, together with roe deer, red deer (Cervus elaphus), and moose (Alces alces)

f.      The limitation and/or regulation of numbers of predators and prey are primarily determined by trophic interactions: e.g. prey density and intraguild interactions, rather than by human intervention, will limit the density of lynx and wolf populations

g.     The system is able to exist in a dynamic state, fluctuating under the influence of climate, disease, and other external factors

Appendix III: California Department of Fish and Wildlife DEPARTMENTAL BULLETIN Defined (Human/Wildlife Interactions in California: Mountain Lion Depredation, Public Safety, and Animal Welfare - Amendment to Department Bulletin 2013-02 2017)

Stepwise Process for Mountain Lion Incidents in the Implementation Areas

First Depredation Event

1. Confirmation of Depredation

a.     Per Fish and Game Code section 4803, a mountain lion depredation must be verified by a responder

2. Oral Authorization

a.     Per Fish and Game Code Section 4805, oral authorization to pursue (haze) the depredating mountain lion may be granted if the immediate pursuit will assist in the noon-lethal removal of the mountain lion from the property

b.     A depredation permit shall be issued as soon as practical

3. Education

a.     The responder should discuss site-specific options for managing mountain lion depredation with the Reporting Party (RP) and educate the RP regarding mountain lion behavior

b.     Additionally, the responder should communicate that as a condition of any depredation permit, the property owner should institute logistically and economically feasible measures designed to reduce the potential for attracting mountain lions

c.     Potential measures include, but are not limited to:

         i.     Removing the carcass and carcass parts of the depredated animals

                 ii.     Install/repair/replace fencing or other shelter designed to exclude mountain lions from the attractant

                iii.     Removing potential suitable habitat (e.g. cover) from the immediate vicinity by clearing brush or removing lower limbs from shrubbery

4. RP Requests a Permit

a.     If the RP requests a depredation permit, the Department shall issue a permit

b.     The Department should issue a non-lethal depredation permit to pursue/haze the mountain lion

c.     Measures that could be part of a permit include, but are not limited to

         i.     Deploying temporary deterrent systems (e.g., motion-sensitive lighting, loud music)

                 ii.     The use of livestock protection dogs, etc.

d.     Such permits shall explicitly indicate that no mountain lion shall be intentionally killed during this phase of the permitting process

e.     Unique characteristics or specific collar/tag information on suspected lions shall be noted and monitored by the Department when possible

Second Depredation Event: If a mountain lion depredation is reported at the same physical location (e.g. reported on animals owned by the same RP within the same geographic ownership or area) within a time period strongly suggesting a lion’s affinity for the site

1. RP Requests a Permit

a.     If damage is confirmed, and the property owner has demonstrated that all reasonable preventative measures recommended by the Department were implemented, the responder should modify the existing permit or issue a new non-lethal depredation permit specifying additional measures not included in the previous permit (e.g., use of bean-bag shots)

b.     Such permits shall explicitly indicate that no mountain lion shall be intentionally killed during pursuit

Third Depredation Event: Depredation id reported a third time at the same physical location (e.g. reported on animals owned by the same RP within the same geographic ownership or area)

1. RP requests a permit

a.     If damage is confirmed by the Department, the RP has demonstrated that all reasonable preventative measures required in the existing permits were implemented, and the RP requests a lethal depredation permit, the Department shall issue a depredation permit to authorization per Fish and Game Code Section 4805

Terms and Conditions of Mountain Lion Depredation Permits: Only one mountain lion may be killed under a depredation permit

1. In order to ensure that only the depredating lion will be taken, the permit shall:

a.     expire ten days after issuance

b.     authorize the permittee to begin pursuit of the depredating mountain lion not more than one mile from the depredation site

c.     limit the pursuit of the depredating mountain lion to within a ten mile radius from the location of the reported damage or destruction

2. If damage continues to occur following the killing of a mountain lion under a permit, the Department may issue an additional depredation permit or Fish and Game Code Section 4807 may allow for immediate additional take

Tracking of Permits

1. Concluding the incident, the responder shall ensure completion of the reporting requirement and close the incident

2. Reporting shall be complete not more than three business days after the incident is concluded

3. Taken under authority of a depredation permit, the carcass shall be collected by the Department and a necropsy performed


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