By: Mark Tyson, M.S.
One of the big things I stress when speaking with folks
about feral hogs is their intelligence. They tend to persist in good condition
during droughts, heat waves, floods and other adverse environmental
perturbations. How is it that they do so
well? It is because they are adaptable, efficient and effective! In this
article I would like to take a look at each of these characteristics and
provide both text and visual representations of these attributes.
By definition, the word adaptable means to
adjust to new conditions and feral hogs do this very well. Thermoregulation and
feeding are the primary drivers of feral hog activities on the landscape. As
temperatures fluctuate, feral hogs adjust their movements to stay warm or
remain cool. Throughout the year new food resources become available on the
landscape as the seasons progress. Feral hogs are quick to acclimate to the
seasonal availability of a new food resource. A study conducted in the Rolling
Plains ecoregion of Texas (Lucia et al. 1999) evaluated the seasonal diets of
feral hogs. Spring diets reflected a high use of vegetation, summer diets
contained 49% soft mast, fall diets were dominated by grain crops and
invertebrates, while winter diets consisted primarily of vegetation. The
researchers found that feral hog diets shifted between seasons in conjunction
with abundant food resources. After
large rainfall events, feral hog rooting can often be observed along roadsides.
The paved surfaces shed additional water into the ditch which in turn hosts a
greater density of healthy plants when compared to upland sites, especially
during dry conditions. I recently observed a sounder of feral hogs feeding on
the seed heads of several roadside grass species while immediately adjacent
upland sites contained lower densities of mature grass species. Ultimately feral
hogs are very adaptable when it comes to their diet.
(Foods of Feral Hogs)
The
adaptability of feral hogs also relates to their interactions with man. Hogs
quickly learn which areas are dangerous and which ones are not. In some places,
feral hogs make extensive forays into open areas and urban properties to feed
because they are not being pressured. Adversely, some property owners only
evidence of feral hogs is the damage they leave behind. One researcher shared a
recent observation he had while studying quail on a north Texas ranch. The
landowner asked him to harvest any feral hog he saw but warned him to be very
accurate if he did decide to shoot. It turns out that the feral hogs actually
integrated into the cow herd as they fed on range cubes across the pasture. The
hogs made the connection between the range cubes as a rich food source and
moving with the cow herd to avoid being shot at.
(Feral Hog Avoiding a Trip Wire)
The
boar pictured in the upper left corner appears to be “sizing up” the trip wire
on this corral trap. It seems that he has made the connection that if the wire
is hit it will cause the door to close. As shown in the photo, this boar looks
as if he has learned that he has to jump the wire to access the bait and leave
the trap unharmed. These examples of the adaptability by feral hogs could be
supplemented by many other examples.
Efficient
By definition, being efficient reflects the act of achieving
maximum productivity with minimum wasted effort. The efficiency of feral hogs
can be reflected in many ways. One of the more prominent displays of efficiency
by feral hogs is reflected in their movements. The area of land an animal
regularly travels in search of food or mates is considered its home range.
Feral hog home ranges are often a reflection of habitat quality and food
availability. In years of plenty, home ranges shrink and in years of scarcity, home
ranges increase. Home range also fluctuates regionally and between genders.
Research conducted in the eastern half of Texas reported that feral hog home
ranges average around 1366 acres (Gabor et al. 1999, Schlichting et al. 2011,
Ilse and Hellgren 1995, Mersinger and Silvy 2007). One research project
conducted in the western half of Texas reported a feral hog home range of
12,355 acres (Adkins and Harveson 2007). The variation between each half of the
state reflects regional differences in habitat. Generally speaking, the eastern
half of Texas is considered mesic (moist) while the western half of the state
is considered arid (dry); therefore feral hogs in western Texas have to cover
more ground to meet their needs. Home ranges also vary between males and
females. Messinger and Silvy (2007) reported male home ranges of 3905 acres
while females ranged over 1606 acres. Gompper (1997) suggested that males
maintain larger home ranges to maximize their reproductive success. This study
also found that the distance moved by feral hogs from water sources and
screening cover increased during the winter and spring due to milder
temperatures. In this instance, the feral hogs made efficient use of the cooler
months by traveling greater distances from their core areas to feed.
Efficient use of available food resources is
highly beneficial to feral hogs, allowing them to gain weight and successfully
reproduce. The picture below represents the locations of a specific feral hog
on an area of land during the fall of 2004.
(Movements of a Radio-marked Feral Hog)
The green dots represent the feral hog’s location at a
specific point in time. Notice the more scattered green dots represent typical feral
hog habitat use in both low land and upland areas. The large cluster of dots
represents a different situation. In this case the feral hog is concentrating
on a crop production area with its movements shadowing the center pivot
irrigation system. More than likely the food available in the crop production
area was more nutritious than the foods available on the rangeland areas which
surrounded it. This is an example of a feral hog effectively using the
landscape and the resources it contains. By utilizing rich food resources and
moving during favorable times, feral hogs make the most of the resources
available while minimizing energy expenditure.
Effective
Being effective reflects success in producing a desired
result. Survival and procreation are the primary goals of all organisms. Annual
survival rates of feral hogs range widely in published studies, ranging between
40% and 80% (Hayes et al. 2009, Adkins and Harveson 2007). These survival rates
are impacted by many external factors such as human influence, diseases and
environmental conditions. Due to their high level of intelligence, feral hogs
are quite effective at avoiding humans. One example of this avoidance behavior
was shared with me by a local feral hog aerial gunning company. Typically, when
pursued with a helicopter, the hogs would run from woody cover into open areas
where they could be easily harvested. Recently
they are observing that some feral hogs hold tight in wooded cover and refuse
to be pushed into open areas, effectively avoiding harvest by traditional
aerial hunting strategies. Additional ground based pursuit would be needed to
flush the hogs from cover.
Recent research conducted by Texas A&M University
suggests that feral hog populations in Texas are experiencing a 16% annual
population growth rate at current harvest levels. Current population estimates
in Texas suggest 2.6 million feral hogs currently occupy the state. Estimates
suggest the Texas feral hog population will increase to 5.2 million by 2015 if
current harvest levels remain the same. On the reproduction front, feral hogs
are doing quite well!
(Table Representing Texas Feral Hog Population Growth Based on Harvest Rates)
Summary
Because feral hogs are adaptable, efficient and effective
they will persist with us into the future. Goals of feral hog eradication can
be attained only where isolated populations exist. Although they cannot be
eradicated, their impacts can be abated. Higginbotham et al. (2008) reported a
66% reduction in agricultural damage by feral hogs after two consecutive years
of control efforts conducted by USDA Wildlife Services on 223,000 acres. The
main thing is to stay active with feral hog population reduction efforts, as
doing nothing will accomplish exactly that. In this instance, it will result in
a 2015 Texas population of 8.6 million feral hogs which is definitely something
to be concerned about!
The hyper-linked resource document below will provide you with quick access to many of our online feral hog resources including publications, fact sheets and videos.
The hyper-linked resource document below will provide you with quick access to many of our online feral hog resources including publications, fact sheets and videos.
For free educational
programming or technical assistance with feral hogs please contact us:
Mark Tyson,
South and Southeast Texas, 979-845-4698, mark.tyson@ag.tamu.edu
Dan Gaskins,
Central and North Central Texas, 254-248-0532, dan.gaskins@tamu.edu
Our services
are provided free of charge through a Clean Water Act 319(h) non-point sources
grant from the Texas State Soil and Water Conservation Board and the U.S.
Environmental Protection Agency