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mtmuley,
Thanks for your private message and your responses here.
Did you read the sources I provided?
Understanding Predation | New Mexico State University - BE BOLD. Shape the Future.
Predation is a much misunderstood ecological process. Most people confuse the act of predation with the effect, believing that the killing of an individual animal invariably results in a negative impact on the population. This view is frequently wrong, and ignores the complexity of predation at...aces.nmsu.edu
"This leads to the most common misconception people have regarding predation, namely that the individual killed by the predator would still be alive if the predator was removed. This simplistic view is used, for example, to justify many predator control programs, and ignores the concepts of predisposition and compensatory mortality. Simply, if predisposition is present, the individual killed by the predator was likely to have died from some other cause anyway. To illustrate, research in New Mexico has shown that individual mule deer killed by pumas were in significantly poorer condition than the population as a whole (Bender and Rosas-Rosas, 2016). This illustrates predisposition; such individuals were increasingly likely to die from some other factor if not killed by a puma. Hence, mortality in these populations was primarily compensatory (Figure 4; Bender and Rosas-Rosas, 2016). Primarily compensatory predation was similarly seen with pronghorn (Antilocapra americana), elk, and desert bighorn (Ovis canadensis) across multiple populations in New Mexico (Figure 4)."
"The direct effect of predation at the level of the individual is that an individual is either killed by a predator or not (potential indirect effects of predation are addressed below). Whether that individual is killed or not often depends upon its degree of predisposition. In other words, is there some characteristic of that individual that makes it more or less likely to be killed by a predator? Many factors can predispose individuals to predation or any other cause of death. For larger animals, perhaps the most important of these is nutritional or body condition (Hanks, 1981; Mech and Peterson, 2003; Bender and Rosas-Rosas, 2016). Individuals in poor shape are more vulnerable for many reasons, including less ability to fight or flee, less environmental awareness and hence less ability to detect the presence of a predator, greater susceptibility to disease and accidents, etc. Other traits can also predispose individuals to predation, including age, debilitation (i.e., injury), and diseases such as chronic wasting disease (CWD) (Errington, 1967; Mech and Peterson, 2003; Mech, 2012; Krumm et al., 2010)."
Wisconsin DNR
"Many deer hunters tend to believe that every deer killed by a predator results in one less deer available for a human hunter to harvest. Research has found the truth to be more complicated. Predators do not, in fact, always reduce the population growth rates of prey. Biologists use the terms “compensatory” and “additive” to describe the impact of predation on any given wildlife population. If predation is “compensatory,” it means the total number of prey to die in any given year does not change as a result of predation. It means the predators remove the number of animals that would have been lost anyway to other causes."
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Thanks for making it easier for us to get a wolf season here, Wisconsin. Super helpful.
Thanks for that.
I am trying to think of a real world example of compensatory mortality with big game animals but coming up short.
I go back to fawns and calves. I don’t see how their mortality could possibly stay the same as the number of predators and therefore predation rise. I thought fawn and calf recruitment was an important part of ungulate population dynamics.
It’s hard because it doesn’t make sense.Why is this hard? Just a lifeboat effect after all. Compensatory mortality on juveniles is particularly common.
Thanks for that.
I am trying to think of a real world example of compensatory mortality with big game animals but coming up short.
I go back to fawns and calves. I don’t see how their mortality could possibly stay the same as the number of predators and therefore predation rise. I thought fawn and calf recruitment was an important part of ungulate population dynamics.
We don’t have wolves down here and that is fine with me. Between mismanagement, poaching, feral hogs, disease, and habitat degradation, the game populations around me have enough to deal with.
Please don’t tell some of the FB hunting groups I am a member of that we don’t have wolves though. Wolves and black panthers or rampant according to a lot of folks down here. Wouldn’t want to ruin a good chunk my entertainment by educating them.
70% died or 70% of those that died, died of predation.It’s hard because it doesn’t make sense.
There was a recent study done here, where over 3 years, 70% of the whitetail fawns in the study died due to predation.
It is going to be a tough sell to ever convince me that the 70% of fawns being eaten by bears, bobcats, and coyotes, would just have died because of something else if they hadn’t been eaten.
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Thanks for making it easier for us to get a wolf season here, Wisconsin. Super helpful.
Mortality in young of the year across most species of wild animal is extremely high under normal conditions. This is almost universal. They succumb to all kinds of things- general unthriftiness or birth defects, drowning, weather, exposure, accidents, predation, bad moms, siblicide, you name it. People have a hard time with this concept because obviously for us, reality is the exact opposite. Almost none of our young die, and that is a huge anomaly in nature.Thanks for that.
I am trying to think of a real world example of compensatory mortality with big game animals but coming up short.
I go back to fawns and calves. I don’t see how their mortality could possibly stay the same as the number of predators and therefore predation rise. I thought fawn and calf recruitment was an important part of ungulate population dynamics.
Thank you! That would be outstanding.I can go through some of my papers and PM them to you. It's a topic addressed by wildlife biologists as it is complex. You can have some areas with additive predation, other areas with compensatory, or some areas with both additive and compensatory. You can even have local populations experiencing both among different age classes.
This is spot on !Mortality in young of the year across most species of wild animal is extremely high under normal conditions. This is almost universal. They succumb to all kinds of things- general unthriftiness or birth defects, drowning, weather, exposure, accidents, predation, bad moms, siblicide, you name it. People have a hard time with this concept because obviously for us, reality is the exact opposite. Almost none of our young die, and that is a huge anomaly in nature.
Figuring out the where the threshold lies between predation removing animals that would have died anyway, and predation becoming additive requires data on mortality, predators, vital rates, etc. Without these data, all of this debate about wolf predation being compensatory or additive is purely speculative. It could be either...or both...depends on the situation.
You personally participate in a real world example of compensatory mortality in big game animals all the time. Hunting seasons and harvest have been managed using this concept for decades.
Straying a little from the wolf issue but since hunters as a group tend to struggle with this idea, here’s an article that is relatively easy reading that illustrates predation and compensatory mortality in fawns:
What is Killing America’s Fawns?
Many hunters picture coyotes scouring woodlots from May to June, snatching newborn fawns between sun-dappled trilliums, and heading home with a hindquarter clamped between their jaws. Why wouldn’t we envision such scenes? Trail cameras across the U.S. often snap grip-and-grins of coyotes, bobcats...www.themeateater.com
The key take-away...even though predation is identified as the leading cause of mortality in many studies, the overall mortality rates differ very little between areas with predation as the leading cause of mortality and areas without predation as the leading cause. That is what compensatory mortality looks like, in a very simplistic nutshell.
70% that died, died of predation.70% died or 70% of those that died, died of predation.
Starvation, trucks, and many others make for a lot of compensatory mortality.
Do you hate bears as more than wolves. You should. They kill way more fawns. This is true just about anywhere there are black bears and ungulate offspring. Why do they get a pass from everyone?
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You personally participate in a real world example of compensatory mortality in big game animals all the time. Hunting seasons and harvest have been managed using this concept for decades.
...
Thank you!Mortality in young of the year across most species of wild animal is extremely high under normal conditions. This is almost universal. They succumb to all kinds of things- general unthriftiness or birth defects, drowning, weather, exposure, accidents, predation, bad moms, siblicide, you name it. People have a hard time with this concept because obviously for us, reality is the exact opposite. Almost none of our young die, and that is a huge anomaly in nature.
Figuring out the where the threshold lies between predation removing animals that would have died anyway, and predation becoming additive requires data on mortality, predators, vital rates, etc. Without these data, all of this debate about wolf predation being compensatory or additive is purely speculative. It could be either...or both...depends on the situation.
You personally participate in a real world example of compensatory mortality in big game animals all the time. Hunting seasons and harvest have been managed using this concept for decades.
Straying a little from the wolf issue but since hunters as a group tend to struggle with this idea, here’s an article that is relatively easy reading that illustrates predation and compensatory mortality in fawns:
What is Killing America’s Fawns?
Many hunters picture coyotes scouring woodlots from May to June, snatching newborn fawns between sun-dappled trilliums, and heading home with a hindquarter clamped between their jaws. Why wouldn’t we envision such scenes? Trail cameras across the U.S. often snap grip-and-grins of coyotes, bobcats...www.themeateater.com
The key take-away...even though predation is identified as the leading cause of mortality in many studies, the overall mortality rates differ very little between areas with predation as the leading cause of mortality and areas without predation as the leading cause. That is what compensatory mortality looks like, in a very simplistic nutshell.
70% that died, died of predation.
The main predator was black bears. Something along the lines of 80% if I am not mistaken.
I don’t hate wolves or bears. Quite the contrary actually. I am in the minority here in that I don’t mind the recently delisted Louisiana black bear being around. I am fascinated by them.
My concern overall and with the study I was speaking of is that the study stated that predation by black bears in the study area was not detrimental to the deer population. I am trying to understand that conclusion.
The decline of the deer population in the study area, which happens to be a place with which I am intimately familiar, has me and many others looking for answers and solutions.
Wolves have a right to eat no doubt about it. I wonder in that instance how many less deer would be donated to food banks etc.Maybe in any zone with enough wolves to hunt, the state should eliminate doe/elk cow tags?
Good question but irrelevant. If hunters think wolves are killing too many deer then they can hunt wolves but also need to stop shooting the manufacturers. Why are hunter shooting does to donate to food banks? That is a little disturbing.Wolves have a right to eat no doubt about it. I wonder in that instance how many less deer would be donated to food banks etc.
That would go over like the proverbial turd in the punch bowl I'm sure.Maybe in any zone with enough wolves to hunt, the state should eliminate doe/elk cow tags?