August 17, 2019

Can coyote predation risk induce reproduction suppression in white-tailed deer?

Abstract

Predators can have powerful nonconsumptive effects on their prey by inducing behavioral, physiological, and morphological responses. These nonconsumptive effects may influence prey demography if they decrease birthrates or increase susceptibility to other sources of mortality. The Reproductive Suppression Model suggests that iteroparous species may maximize their lifetime reproductive success by suppressing their reproduction until a future time, when conditions may be more favorable. Coyote (Canis latrans) range expansion in the United States has exposed white-tailed deer (Odocoileus virginianus) populations to increased predation risk, and coyote predation can have profound effects on white-tailed deer reproductive success. We evaluated effects of temporal variation in predation risk (i.e., coyote–deer ratios) on fecundity and reproductive success of white-tailed deer on the Joseph W. Jones Ecological Research Center in southwestern Georgia, United States, by exploiting a rapid decline in coyote abundance to establish a natural experiment. We measured fecundity by examining ovaries for evidence of ovulation, and measured reproductive success using evidence of lactation from deer harvested before and after the decline in coyote abundance. We found that incidence of ovulation and lactation increased following the decline in predation risk. Our results suggest coyotes may be able to influence deer recruitment, independent of direct predation, through interactions that result in reduced fecundity. More broadly, our study suggests that in order to understand the totality of the effect of predators on prey population dynamics, studies should incorporate measures of direct and indirect predator effects.<<<Read More>>>

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Jim Beers’ Rebuttal: Why Recruit Hunters?

*Editor’s Note* This information has been provided by Jim Beers.

The following letter to the editor by a reader of the St. Pail Pioneer Press poses a question well worth considering and answering. What follows his letter is a letter I submitted to the St. Paul Paper in response. Since such letters require brevity, please forgive my less than comprehensive treatment of this matter. Jim Beers 14 Oct.

*Note* – Not fully knowing the copyright infringement rules of the Pioneer Press, I opted instead to provide just a link back to the original Letter to the Editor.

A SELECTIVE SERVICE FOR HUNTERS?

Recently a reader challenged DNR Commissioner Landwehr’s commitment to “recruit more hunters”. Although by reading between the lines I suspect the author is what might be termed an “anti-hunter”, I find myself (an avid hunter) in partial agreement with his position.

I disagree with his statement that, “If the DNR needs more money, just raise the subsidized fees on the current hunters”. In truth the DNR wildlife folks, like other state’s wildlife agencies, and unlike other state functions like Parks, are almost entirely supported by excise taxes on arms, ammunition, archery products, and fishing tackle/products (termed “user fees”) PLUS the license revenue from state licensing of hunters and fishermen. That the wildlife agencies get or require “subsidies” is due to all the non-revenue producing and mandated activities like wolves, songbirds, native species and other activities that appear as somehow worthy but are, in fact, intended to overwhelm and replace hunting and fishing management by state governments.

I do however agree with his incisive question that since “the state doesn’t recruit more golfers” etc., “Why do the fish and wildlife sectors of our economy need to be subsidized by the general population?” As he correctly observes, limits could be “increased” and fees could be “raised” although the latter, like raising taxes, would likely backfire and ultimately result in lower revenue as people adjust. Hunters and fishermen are free Americans, not pawns of the state.

The real answer to “why” is state bureaucrats’ pay, promotions, bonuses, retirement and growth. It is all the Ducks Unlimited’s and Pheasants Forever’s memberships and staff’s pay and benefits. It is the sporting’s goods dealers and their business. It is the federal bureaucrats and all the “strings” they have on state agencies that have made them little more than federal subcontractors. Finally, it is all those state and federal politicians and “wannnabee”-politicians that reap votes and support from unsuspecting hunters and fishermen as they pander to the illusion that catering to the anti-hunters and anti-fishermen is somehow good for hunters, fishermen and the cultural traditions and sport they so love.

Jim Beers
14 October 2013

If you found this worthwhile, please share it with others. Thanks.

Jim Beers is a retired US Fish & Wildlife Service Wildlife Biologist, Special Agent, Refuge Manager, Wetlands Biologist, and Congressional Fellow. He was stationed in North Dakota, Minnesota, Nebraska, New York City, and Washington DC. He also served as a US Navy Line Officer in the western Pacific and on Adak, Alaska in the Aleutian Islands. He has worked for the Utah Fish & Game, Minneapolis Police Department, and as a Security Supervisor in Washington, DC. He testified three times before Congress; twice regarding the theft by the US Fish & Wildlife Service of $45 to 60 Million from State fish and wildlife funds and once in opposition to expanding Federal Invasive Species authority. He resides in Eagan, Minnesota with his wife of many decades.

Jim Beers is available to speak or for consulting. You can receive future articles by sending a request with your e-mail address to: jimbeers7@comcast.net

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Is Maine’s Whitetail Deer Age Structure Changing?

*Editor’s Note* The graph and information below was crafted by contributor Richard Paradis from information provided by me in addition to his own information.

One of the most telling events that can occur in a deer herd is a change in age structure. In brief, age structure is a dynamic investigation into the complete breakdown of how many deer make up specific age categories. We are often discussing the relationship between male and female deer as well as the number of fawns (new born) in relation to the number of adult female deer. Seldom, or at least not to the same degree, is the age structure of a deer herd discussed.

A well educated and experienced biologist, providing they have been able to collect the necessary data, can tell what percentage of a deer herd makes up fawns; up to 1 and 1/2 years of age, young deer; 1 and 1/2 to 3 and 1/2 years old, and mature deer; over 3 and 1/2 years. The same biologist should know, according to the geographic information, as well as available habitat, etc. what the age structure of a herd should be in order to classify it as healthy and to make determinations as to what any harvest should be like for the upcoming hunting season based on herd structure and trends.

There can also be certain movements in that age structure that can indicate to the biologist that something is changing, alerting them to the need to investigate what those influences might be and make changes to the management strategies to maintain a viable and healthy herd.

Some people believe that in order to destroy a deer herd, something has to kill off all the deer, adults included. This is not entirely true. In theory, if there were never any new born deer to add to the herd and in combination with all other mortality to the deer herd, how long do you think it would be before the deer herd disappeared? Not long.

In this kind of scenario, an examination of the age structure might alert us to what could be happening. For the sake of discussion, let’s say a healthy deer herd looked something like this: fawn recruitment, that is the percentage of new born fawns that live to see their first winter, is 20% of the herd; Young deer, 1 and 1/2 – 3 and 1/2 years 50% and mature deer 30%.

In an attempt to keep this as simple as possible, let’s say that with the above situation of 20%, 50% and 30%, the average age of the deer is 2.9 years. If you played around with those percentages you would soon discover that it takes quite a dramatic change in those percentages to effect a noticeable move in the average deers’ age.

As an example, let’s say that in one year, the fawn recruitment was wiped out, i.e. 0%. That would increase the average age of the deer to approximately 3.3 years (I divided the 20% loss evenly between the remaining two age groups). Notice that what appears to be a rather small change in average age (less that 1/2 year), a complete loss of fawn recruitment is a devastating event. If we carried that out for a few years, where fawn recruitment remained at 0%, we can see that the age of the deer herd gets older and older. Once this is discovered, trust me, I think the deer herd is in trouble.

As far as Maine’s age structure for deer, I don’t have the kind of data necessary to calculate age structure and I’m not sure whether the Maine Department of Inland Fisheries and Wildlife(MDIFW) does either. I am assuming they must. What I did do is to extract some of the data that MDIFW provides in their deer harvest information to use to see if there can be determined any trends in age structure.

All that is available on the MDIFW website is harvest information beginning in 2005 through 2011. In each of these reports, MDIFW provides in their harvest data the percentage of take based on the same age classifications I have used above, i.e. fawn, young and mature. I pulled out of these reports those percentages and listed them by year. Mr. Paradis was kind enough to compile them into a graph for better visual comparison.

However, bear in mind a few things. The data extracted may not be a clear representation of the entire herd of Maine’s deer. This is harvest data only and there are restrictions to the sex and age of what deer can be taken and in what geographical regions. Therefore, the only way we can make good comparisons is with the ability to compare those items that remain constant.

In theory, if we had for these seven years the same number of “Any-Deer Permits” in all the same regions, this harvest data would be a bit more accurate and reliable for my purposes. However, the changes in the issuing of Any-Deer Permits did not change drastically statewide until 2009 when Any-Deer Permits were halted in Northern, Western and Downeast Maine and again for the 2011 deer hunting season. As such, I’m not sure exactly how to use harvest data for 2010 and 2011 in comparison with all previous years.

From the graphs and information below, you can clearly see the percentage of Young and Mature deer taken for each of the years listed, 2005-2011. Over the span of the seven years, the average percentage of Young deer harvested is 46.4% and for Mature deer, 20.4%.

Not really knowing how to handle the 2010, 2011 harvest data, one could conclude that there is a slight trend upward in the age structure according to harvest information. Is this something to be concerned about. I would think so. Is MDIFW keeping an eye on this data and any trends? I certainly hope so. If the age structure of Maine’s deer herd is on the increase, there has to be a reason, which is generally related directly to fawn recruitment. Without good fawn recruitment a deer herd is doomed. Depending upon the severity of that loss, will determine how quickly a herd becomes decimated.

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