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Whitetail Deer / No faith in the SAK numbers
« on: November 20, 2007, 10:06:26 AM »
Recently I have been looking at car deer crashes as an indicator of the deer herd size in WI. If the population is high, then we should be seeing increased car deer collisions. Driver data indicates that the number of miles driven increases about 2% a year due to new drivers and new roads. Miles driven is on the increase. The math is simple. The number of miles drives is on the increase and based on the SAK formula, so is the deer herd. The last few years we have been at all time highs of 1.6 - 1.8 million. Pretty easy right? More miles driven plus more deer should equal more car deer crashes.
I did not stop at WI. I also looked at other states to see if they were seeing the same percentage change in the last few years. I used the data from 2004 to 2006 since that is when EAB took off and we would be seeing the effects of the T-zone hunts.
Wisconsin Data
2002: 45,278 car/deer crashes , deer herd estimate (pre hunt) 1.3M
2003: 47,840 car/deer crashes , deer herd estimate (pre hunt) 1.6M
2004: 48,316 car/deer crashes , deer herd estimate (pre hunt) 1.6M, steady increase, right?
2005: 41,688 car/deer crashes , deer herd estimate (pre hunt) 1.6M
2006: 36,900 car/deer crashes , deer herd estimate (pre hunt) 1.8M
As you can see, the 2006 data shows a 25% drop in car deer collisions from 2004 to 2006 and yet the SAK numbers claim 1.8 million deer yet we were seeing a steady increase in crashes from 2002 to 2004. The data from 2006 shows that with the with the deer herd at an all time high and miles driven across the state at its highest amount ever, we are seeing deer/car crashes at their lowest since those of 1999. I believe the number of miles driven is accurate but I have a problem with the SAK deer herd number and the car/deer crashes show that.
Next, I looked at other states to see if they were seeing the huge declines in car/deer crashes like WI
Illinois Data
2000, 19,731 car deer crashes
2001, 22,933 car deer crashes
2002, 23,675 car deer crashes
2003, 25,660 car deer crashes
2004, 25,837 car deer crashes
2005, 24,248 car deer crashes
2006, 25,491 car deer crashes
Net change in last two years of just 1.5%
Michigan Data
2000, 65,005 car deer crashes
2001, 66,993 car deer crashes
2002, 63,136 car deer crashes
2003, 67,760 car deer crashes
2004, 62,707 car deer crashes
2005, 58,741 car deer crashes
2006, 60,875 car deer crashes
Net change in last two years of just 3%
Iowa Data
2000, 7556 car deer crashes
2001, 6,057 car deer crashes
2002, 8,641 car deer crashes
2003, 8,396 car deer crashes
2004, 8,481 car deer crashes
2005, 7,320 car deer crashes
2006, 8,335 car deer crashes
Net change in last two years of just 2%
New York saw a 1% decline in the last year
Ohio saw a 1% increase in car deer crashes in the last two years. Minnesota is the only state that is seeing a decline nearly every year since 1999 but it's numbers vary greatly from year to year. On average, other states are seeing pretty static numbers of car/deer crashes (around 1 to 2 % ) and yet Wisconsin's numbers have dropped dramatically.
Side note: All the states that I looked at saw a drop in car deer crashes in 2005 and then saw an increase in 2006. All states except WI which continued to decline.
Being a skeptic myself, I started to look at WI county totals. This was hard since few counties have just one DMU that covers it entirely plus from year to year, most saw some sort of change. I went back to the reg books and the DMU maps from 2002 to present time. I started with Waupaca county since it has been a T-zone or EAB county for many years. Waupaca County is covered by deer management units 62A, 63A and 65B. I looked at the car/deer crash totals for Waupaca County starting with 2001
2001, 1954 car/deer crashes
2002, 2164 car/deer crashes
2003, 2409 car/deer crashes .. Are you seeing the trend? Now insert T-zones and EAB
2004, 2333 car/deer crashes
2005, 1701 car/deer crashes
2006, 1943 car/deer crashes which is a 17% decrease from 2004
Next, I looked at Buffalo County which is covered almost entirely by DMU 61. Like Waupaca county, Buffalo county has been a T-zone or EAB county since 2003.
Buffalo county
2001, 402 car/deer crashes
2002, 327 car/deer crashes
2003, 445 car/deer crashes
2004, 349 car/deer crashes
2005, 312 car/deer crashes
2006, 301 car/deer crashes which is a 14% decrease from 2004
Ok so now your thinking to yourself, "You said that WI saw a 25% decrease, These Counties are less than that. There must be Counties that saw much bigger decreases in car/deer crashes" Well you would be right. Enter Manitowoc County which is covered almost completely by DMU 64 and has also been a T-zone County since 2003 .
Manitowoc county
2001, 722 car/deer crashes
2002, 709 car/deer crashes
2003, 833 car/deer crashes
2004, 962 car/deer crashes
2005, 634 car/deer crashes
2006, 526 car/deer crashes which is a 45% decrease from 2004
If you have kept up this far, thanks. we are almost done. The next question you should be asking is "Hey! what about those counties that have never been part of the T-zone or EAB structure, surely they too are seeing the same declines in car/deer crashes?" Good question. Again, it was hard to find a county that was spared from any change over the years but I did find Forest County which is covered by DMU's 38,39,43,44 and 45. Forest County has remained a regular deer season County through all of the season structure changes so it was a good control unit to use as a check
Forest County
2001, 124 car/deer crashes
2002, 139 car/deer crashes
2003, 210 car/deer crashes
2004, 159 car/deer crashes
2005, 183 car/deer crashes (actually saw a 15% increase of crashes)
2006, 155 car/deer crashes which is a 2.5% change from 2004 and aligns with what other states are seeing.
So, there you have it. The reason why I no longer have faith in the SAK (at least since 2001) Back when it was pure data from a regular season structure, it was much closer to estimating the herd size but in early 2000 when T-zones, EAB, CWD hunts and youth hunts started to screw with the kill totals, it became useless and is estimating higher herd numbers than what is actually out there.
I did not stop at WI. I also looked at other states to see if they were seeing the same percentage change in the last few years. I used the data from 2004 to 2006 since that is when EAB took off and we would be seeing the effects of the T-zone hunts.
Wisconsin Data
2002: 45,278 car/deer crashes , deer herd estimate (pre hunt) 1.3M
2003: 47,840 car/deer crashes , deer herd estimate (pre hunt) 1.6M
2004: 48,316 car/deer crashes , deer herd estimate (pre hunt) 1.6M, steady increase, right?
2005: 41,688 car/deer crashes , deer herd estimate (pre hunt) 1.6M
2006: 36,900 car/deer crashes , deer herd estimate (pre hunt) 1.8M
As you can see, the 2006 data shows a 25% drop in car deer collisions from 2004 to 2006 and yet the SAK numbers claim 1.8 million deer yet we were seeing a steady increase in crashes from 2002 to 2004. The data from 2006 shows that with the with the deer herd at an all time high and miles driven across the state at its highest amount ever, we are seeing deer/car crashes at their lowest since those of 1999. I believe the number of miles driven is accurate but I have a problem with the SAK deer herd number and the car/deer crashes show that.
Next, I looked at other states to see if they were seeing the huge declines in car/deer crashes like WI
Illinois Data
2000, 19,731 car deer crashes
2001, 22,933 car deer crashes
2002, 23,675 car deer crashes
2003, 25,660 car deer crashes
2004, 25,837 car deer crashes
2005, 24,248 car deer crashes
2006, 25,491 car deer crashes
Net change in last two years of just 1.5%
Michigan Data
2000, 65,005 car deer crashes
2001, 66,993 car deer crashes
2002, 63,136 car deer crashes
2003, 67,760 car deer crashes
2004, 62,707 car deer crashes
2005, 58,741 car deer crashes
2006, 60,875 car deer crashes
Net change in last two years of just 3%
Iowa Data
2000, 7556 car deer crashes
2001, 6,057 car deer crashes
2002, 8,641 car deer crashes
2003, 8,396 car deer crashes
2004, 8,481 car deer crashes
2005, 7,320 car deer crashes
2006, 8,335 car deer crashes
Net change in last two years of just 2%
New York saw a 1% decline in the last year
Ohio saw a 1% increase in car deer crashes in the last two years. Minnesota is the only state that is seeing a decline nearly every year since 1999 but it's numbers vary greatly from year to year. On average, other states are seeing pretty static numbers of car/deer crashes (around 1 to 2 % ) and yet Wisconsin's numbers have dropped dramatically.
Side note: All the states that I looked at saw a drop in car deer crashes in 2005 and then saw an increase in 2006. All states except WI which continued to decline.
Being a skeptic myself, I started to look at WI county totals. This was hard since few counties have just one DMU that covers it entirely plus from year to year, most saw some sort of change. I went back to the reg books and the DMU maps from 2002 to present time. I started with Waupaca county since it has been a T-zone or EAB county for many years. Waupaca County is covered by deer management units 62A, 63A and 65B. I looked at the car/deer crash totals for Waupaca County starting with 2001
2001, 1954 car/deer crashes
2002, 2164 car/deer crashes
2003, 2409 car/deer crashes .. Are you seeing the trend? Now insert T-zones and EAB
2004, 2333 car/deer crashes
2005, 1701 car/deer crashes
2006, 1943 car/deer crashes which is a 17% decrease from 2004
Next, I looked at Buffalo County which is covered almost entirely by DMU 61. Like Waupaca county, Buffalo county has been a T-zone or EAB county since 2003.
Buffalo county
2001, 402 car/deer crashes
2002, 327 car/deer crashes
2003, 445 car/deer crashes
2004, 349 car/deer crashes
2005, 312 car/deer crashes
2006, 301 car/deer crashes which is a 14% decrease from 2004
Ok so now your thinking to yourself, "You said that WI saw a 25% decrease, These Counties are less than that. There must be Counties that saw much bigger decreases in car/deer crashes" Well you would be right. Enter Manitowoc County which is covered almost completely by DMU 64 and has also been a T-zone County since 2003 .
Manitowoc county
2001, 722 car/deer crashes
2002, 709 car/deer crashes
2003, 833 car/deer crashes
2004, 962 car/deer crashes
2005, 634 car/deer crashes
2006, 526 car/deer crashes which is a 45% decrease from 2004
If you have kept up this far, thanks. we are almost done. The next question you should be asking is "Hey! what about those counties that have never been part of the T-zone or EAB structure, surely they too are seeing the same declines in car/deer crashes?" Good question. Again, it was hard to find a county that was spared from any change over the years but I did find Forest County which is covered by DMU's 38,39,43,44 and 45. Forest County has remained a regular deer season County through all of the season structure changes so it was a good control unit to use as a check
Forest County
2001, 124 car/deer crashes
2002, 139 car/deer crashes
2003, 210 car/deer crashes
2004, 159 car/deer crashes
2005, 183 car/deer crashes (actually saw a 15% increase of crashes)
2006, 155 car/deer crashes which is a 2.5% change from 2004 and aligns with what other states are seeing.
So, there you have it. The reason why I no longer have faith in the SAK (at least since 2001) Back when it was pure data from a regular season structure, it was much closer to estimating the herd size but in early 2000 when T-zones, EAB, CWD hunts and youth hunts started to screw with the kill totals, it became useless and is estimating higher herd numbers than what is actually out there.