A Third of Studied Mississippi Bucks Used Separate Ranges

STEP 1 · Two floodplains

Thirty collared bucks lived on mild river ground

The work ran from 2017 to 2021 on adult male white-tailed deer in central Mississippi. Crews darted males estimated at 1.5 years or older and the paper does not report how those ages were spread. This is not a mature-buck-only result. They kept animals with at least 11 consecutive months of GPS fixes and used a fix every four hours. That filter left 30 bucks and 44 buck-years because some collars covered two years. One site was about 49,000 acres (about 20,000 hectares) of private land on the Big Black River in Madison and Yazoo counties. The other was about 37,000 acres (about 15,000 hectares) of public and private land on the Mississippi River in Issaquena and Humphreys counties. The region averages about 0.6 inch (1.5 cm) of snow a year. The authors set that mild climate against northern herds in which some deer move from summer range to winter ground for forage, dense evergreen cover and easier travel in deep snow.

They sorted bucks by eye from displacement plots and the raw points and they did not use a migration distance chosen in advance. Separated clusters with a strong repeated swing were mobile and the rest were sedentary. Reported size is the annual kernel left whole. Core distance used split segments because some mobile bucks had only one core in that whole kernel.

STEP 2 · Whole range

Two bucks pulled the mobile average far up

Sedentary bucks were 67 percent of the 30 and their mean annual kernel was 892 acres (361 hectares). Mobile bucks were the other 33 percent and their mean annual kernel was about 16,100 acres (6530 hectares). Bucks 27 and 140 were the outliers at about 49,600 acres (20,070 hectares) and about 90,300 acres (36,559 hectares). With those two removed the mobile mean fell to about 2,700 acres (1096 hectares) and the size difference remained in their test. Our read is that the reduced mean is the fairer picture of a mobile buck's whole annual range on these sites. That acreage still holds both clusters. The text we read gives no size for a single segment.

Mobile core centers averaged 4.4 miles (7.1 kilometers) apart and the standard deviation was the same 4.4 miles. The authors also describe some mobile segments separated by a few hundred yards (a few hundred meters). Our read is that 4.4 miles is not a search spacing rule. Use ground where you have actually seen that buck.

Estimated age showed no detectable link to strategy. The authors say a larger sample might still show an age link. A missed link does not prove age never matters. No buck with two years of data switched strategies. By our count that is 14 bucks because 44 buck-years minus 30 animals leaves 14. The paper did not study dispersal. Our read is only that a return after weeks means that gap was not a one-way move.

STEP 3 · Short trips

One-range bucks made more excursions

An excursion was any move at least 0.31 miles (0.5 kilometers) outside the 95 percent kernel. Sedentary bucks averaged 5.9 a year and mobile bucks averaged 0.8. Mobile bucks made few of these trips. When they did, the trips averaged 25.5 hours against 12.7 hours for sedentary bucks. The distance test did not show a clear difference. These data do not establish that one class walks farther on an excursion.

On these sites the paper puts peak breeding at 25 December through 7 January on the Big Black site and 20 December through 2 January on the river site. Excursion timing did not differ between the classes. Excursions ran highest from that breeding peak into early spring and were uncommon from late spring through late summer. The month test on 40 shifts did not detect a peak. Forty shifts spread over 12 months is a modest count, so a moderate monthly peak could have been missed. A missed peak does not prove that month never matters.

STEP 4 · Round trips

Seven mobile bucks also bounced between segments

Seven of the 10 mobile bucks also bounced. A bounce in this paper is a round trip between the two segments during a longer stay. A test of 43 bounces found an uneven month pattern. January held 23 percent and October held 19 percent. The authors write that bouncing peaked in late January just after peak breeding. The results tally bounces by month, so that late-January line is their reading of the January share. They suggest the October bounces may be checks on doe groups in the other segment before breeding.

The authors call the pattern partial migration and say the environmental reason is not clear. They judge hunting risk an unlikely sole driver because many shift dates fell outside the hunting season. Mobile bucks commonly shifted outside floods and several were never near a flooded river. The authors also report a mobile buck leaving an area that another mobile buck occupied days later. Our read is that a new buck on your camera does not show where the first buck went.

STEP 5 · Your log

A return shows he came back to watched ground

Our observation to test is a dated log on one adult buck you can tell apart. Record the last day he is on the cover you watch and the next day you have him again.

Our read is that a gap of a day or two tells you little. Fixes were kept every four hours, and a camera cannot see a half-day trip the way a collar does. A short absence leaves a second core open because seven of the 10 mobile bucks made quick round trips between segments. The paper does not report how long those bounces lasted.

A gap of many weeks followed by a return is consistent with a shift in this sample, but it also fits a buck that stayed nearby and avoided your cameras. The log can show that this buck was missing from watched ground and then present again. It cannot show a second core, a distance or that he belongs to the mobile class. If he is one of the mobile type, he may leave again later that year. Mobile bucks in this sample averaged 2.9 shifts a year.

If he never returns, this paper cannot tell you why. A long stay elsewhere, a death, and time on ground your cameras miss can all look the same. A repeated multi-week gap outside late December and early January fits the authors' report that shifts occurred through the year.

This sample is 30 adult bucks on two central Mississippi river bottoms and 10 were mobile. The authors say strategy is a continuum even though they split the bucks for analysis. The collars did not cover does, fawns, hill country or northern herds that migrate for winter. Our read is that ground on one cluster can still lose a mobile buck for weeks while he uses another core. That is not a promise of a buck on the ground.