NEVADA'S- RUBY- BUTTE STUDY AND SOME FINDINGS ON MULE DEER PRODUCTION A.ND SUPVIVAL Ron Lee

The purpose and tbpic of t h i s r epor t cen te r s on i n t e r p r e t a t i o n s of reproduction and fawn su rv iva l da ta for. t he Ruby-Butte deer herd. A l l too o f t e n we as game managers r e j e c t ideas and f indings because of shakey confcdence l i m i t s , e s t ab l i shed and accepted references t o works, read-in elements of b ias and f e a r of o r i g i n a l f indings . These bases of r e j e c t i o n serve a s good checks and bal- ances, but very seldom do we allow ourselves t o become completely objec t ive with methods o r analys is of information about game problems t h a t a r e unique and i so- l a t ed . This i s the aim of t h i s paper and our Mule Deer Workshop: t o express a l l f indings and opinions ob jec t ive ly i f i t appears v a l i d o r not .

Several methods were employed t o gather information about product iv i ty and su rv iva l f o r t h e Ruby-Butte deer herd. These included year around herd composition, age s t r u c t u r e of a l l harvested deer through check s t a t i o n s , age da ta from deer trapped and tagged and r e t r a p s , in-utero and corpora l u t e a repro- ductive records , spr ing and summer mor ta l i ty searches, cursory body condit ion evaluat ions of trapped deer and co l l ec ted deer , plus c r ipp l ing loss determina- t ions derived from mandatory hunter quest ionnaire r e tu rns (dead and wounded deer recorded by hunters) .

Summer herd composition counts were conducted and recorded by month f o r th ree years s t a r t i n g i n 1968 t o d e t e c t any fawn l o s s and provide a produc- t i o n index. However, inadequate samples plagued an accurate assessment of herd production and fawn loss . This f a i l u r e was centered around inclement weather, s e c r e t i v e doe and fawn behavior and dense vegeta t ion . Even so , the fawnldoe r a t i o increased with each successive month t o a peak fawn r a t i o i n September during a l l t h ree sunpner samples; therefore , September herd composition appears t o be the only near v a l i d sample obtained (Table I ) .

September fawn r a t i o s var ied from 128 i n 1968, and 112 i n 1969, t o 81 f o r 1970. The change i n r a t i o from September t o pos t season (December) a s a l leged loss each year va r i ed from 15% t o 4.5% and no change f o r years 1968-70 respec t ive ly . However, September and December r a t i o s a r e i n f a c t comparable.

Summer, f a l l and spr ing herd composition f indings a r e compiled on the at tached Table I along with herd composition of trapped deer t o r e f l e c t herd product iv i ty . Herd composition r a t i o s f o r trapped deer include newly tagged deer and retraps*. Fawn r a t i o s found among trapped deer were higher (from 8.5 t o 20%) than post season r a t i o s i n every year except 1970 where r a t i o s were 25% l e s s .

The 1969-70 winter was extremely mild and t h i s may have caused such a d ivers ion from normal. b o t h e r implicat ion i s f o r a 27% loss during the December through February period, but f i n a l spr ing fawnladult r a t i o s ind ica te a 15% l o s s and mor ta l i ty searches a l s o r e f l e c t a lower loss .

* Deer tagged during previous years but handled again.

Widely var ied fawn r a t i o s among trapped deer suggest a sample b ias linked perhaps with fawn behavior o r tending toward t r a p shyness o r proneness, thus making fawn r a t i o s inval id . The buckldoe sample appears representa t ive of the e x i s t i n g herd composition because of the c l o s e c o r r e l a t i o n between pos t season and trapped deer buck r a t i o s . The alone tends t o point out the biased va r i ab le among trapped fawn r a t i o s .

TABLE I

DEER HERD PRODUCTIVITY

Trapping Ra t io s Fawns / 100 Does Pos t Season, (Sample) (Retraps & New Deer) March May %

Year J u l y Aug . Sep t . B u c k / ~ o e Fawn/~oe Fawn/~d . B u c k / ~ o e Fawn/~oe Fawn/~d . Fawn/~d . F a w n / ~ d . Loss

67-68 - - - 48 8 0 54 44 96 66 NO DATA - (152) (194) (503) (617)

70-71 12 49 8 1 54 8 2 52 58 9 8 6 3 45 3 7 30.0 (261) (596) (464) (564) (745) (924) (219)

Avg.24.2

PRODUCTIVITY & *AGE COMPOSITION - COLLECTED FEMALE, DEER crl C\I

Fawn 2 - 2% 2 2 2 2% 2 2 5 -2% sf 9 Preg . 1 10 9 16 5 3 1 2 0 4 2

N. Preg . 13 3 1 0 0 0 0 0 0 0 0

Fe tus 1 9 11 2 9 8 - 3 5 - 7 3 (7) (7) (16) (4 - (1) (2) - (4) (2

Aver age - 1.28 1.57 1 .81 2 . 0 - 2 . 5 - 1.75 1 .5

* = A t p rev ious o r c u r r e n t b reed ing season

N. Preg. = Not pregnant

I Preg. = Pregnant Re t r aps = Those d e e r r ecap tu red from prev ious y e a r s o n l y

In-utero and corpora l u t e a da ta a r e compiled on the at tached pages and Table I f o r seventy-one and t h i r t y does r e spec t ive ly . m e average number of f e tuses per pregnant adu l t doe (1% years and o l d e r ) is 1.78. Average f e t u s numbers appear t o increase with each year of age t o gbout the @ year age c l a s s and then tapers o f f . However, sample s i z e could have considerable e f f e c t upon t h i s .

A l l does 3 years o ld and o lde r were found pregnant, A high incidence of breeding yea r l ings is indica ted - 76%. Corpora l u t e a da ta from 30 does used as an ind ica t ion of herd product iv i ty averaged 1.83 per doe. Corpus a lb icans were l e s s d i sce rn ib le and/or frequent with an average of 0.86 per breed doe.

Herd compositicm da ta were compiled during the months of December and March through e a r l y May s ince 1968 t o d iscern tqwn l o s s from lowered fawn/ adu l t r a t i o s expressed i n percent loss (Table I ) . The indica ted fawn loss of 15.7% i n 1970 appears below average aqd fawn l o s s f o r 1969 and 1971 would be considered above average based on the th ree year average l o s s of 24.1%.

Routine mor ta l i ty search t r ansec t s were e s t ab l i shed i n 1969 s t a r t i n g with a severe winter t a gain some ind ica t ipn of loss . Transects were located i n key winter and intermediate ranges. A summary of mor ta l i ty search r e s u l t s i s tabula ted i n the t a b l e belqw.

Miles of Transect Mor ta l i t i e s / Avg. Distance Avg. Ocular Mor ta l i t i e s (Foot & Horseback) Linear Mile t o M o r t . ( ~ t . i Swath E S ~ . ( A . ) per Acre

1971 35 .17 ( 6) 3 5 8 9 .047

( In 1971, Foot t r a n s e c t s only)

Col l ec t i on Number

~ Age J r Y r s . &Mos .

FINDINGS

MULE DEER REPRODUCTIVE DATA

Ovary Pregnancy In-Utero & Condition Status Comments

L

N NP - N NP - M PP - Pr PP - P r P P - M PP - N NP - Pr PP Probable abo r t i on

69 Reproductive Year

1969 - 70 Reproductive Year

G-1 G- 2 G- 2 3- MM 2- FF 2-F & M 2-MM 2- FF 1-F, 1-aborted 2-M & F 2-M & F 2-MM 1- F 2-MM - - Dry mammaries - -

Collect ion Age Ovary Pregnancy In-Utero & Number * Y r s .&Mos. Condition S ta tus Comen t s

7 9 2- 30 8 1 1- 18 82 3-42 8 6 3- 44 8 7 3- 44 88 5-81 8 9 0- 9 9 1 9- 117 9 4 3-44 9 5 3-44 9 6 2- 34 99 9- 107

100 0-11 101 0- 11

1034 Trap Mortal i ty 10+

Spruce Mortal i ty 3% 1826 Mortal i ty 7% Spruce Mortal i ty 9% KA 991 1%

N = Nulliparous M = Multiparous PR = Primiparous

P P P NP NF' P PP NP NP NP NP PP PP NP P P NP

1970 - 71 Reproductive Year

NP = Not pregnant P = P r e g n a n t PP = Post Partern

G-No. = Gastrula pregnancy and No. of f e t u ~ e s

1-F resorbed

1-F abor t ion G- 1

* Age a t previous breeding season

COLLECTION NUMBER

5 3 54 5 5 5 7 5 8 5 9 6 0 62 6 5 6 3 6 6 6 7 6 8 6 9 70 7 1 7 3 74 7 5 7 6 7 7 7 9 8 1 8 2

1034 Mortality Spruce Mortality 182)6 Mortality Spruce Mortality KA991 Mortality

86 8 7 88 8 9 9 1 94 9 5 9 6 99

RUBY- BUTTE DEER HERD PRODUCTIVITY

AGE , CORPORA CORPUS BREEDING SEASON LUTEA ALBICANS

1% 1 1 1% 2 0 3% 2 1 @i 4 1 3% 2 1 2% 2 0 4% 2 2 3% 2 0 1% 2 0 Fawn 1 0 Fawn 0 0 1% 1 1 1% 0 1 Fawn 0 0 Fawn 0 0 2% 0 0 6% 2 1 2% 0 1 Fawn 0 1 6% 2 1 Fawn 0 0 2% 2 0 Fawn 1 0 3% 2 1 lo+ 2 2 3% 2 0 7% 3 2 9% 2 1 1% 1 0 3% 2 1 % 2 0 6% 3 1 Fawn 0 0 9% 2 1 3% 2 1 3% 1 2 2% 2 1 9% 3 2

A t o t a l 05 35 mi les of r o u t i n e t r a n s e c t s f o r 1971 found s i x mor t a l i - t i e s f o r a per l i n e a r mi le f i g u r e of 0.17. This f i g u r e compares wi th t h e 0.12 per mi le f i g u r e found i n 1970, b u t t h e 1971 per ac re f i g u r e o f ,047 m o r t a l i t i e s sugges ts a c l o s e comparison with t h e m o r t a l i t y r a t e of .055 per ac re i n 1969. Tib ia bone marrow c h a r a c t e r i s t i c s f o r most m o r t a l i t i e s found i n 1969 and 1971 d isp layed m a l n u t r i t i o n s t r e s s . Based on a sample of 48 m o r t a l i t i e s wi th d i s c e r n i b l e ages t h e r e were 37.5% fawns, 16.7% y e a r l i n g s , 18.7% 2 year o l d s , 10.4% 3 year o l d s , no 4 o r 5 year o l d s , 21% 6 yea r o l d s , and 14.6% 7 yea r s o ld and o l d e r .

Quest ionnaire ha rves t and younded and dead deer information was p l o t t e d by period* of t h e dee r seasons f o r 1968, 1969 and 1970 on t h e a t tached graphs (Figures 1-3) t o he lp po r t r ay c r i p p l i n g l o s s . This is used t o po in t o u t an a l l eged d i r e c t r e l a t i o n s h i p between c r i p p l i n g l o s s (dead and wounded deer repor ted seen) and ha rves t o r hunt ing p re s su re . I f dup l i ca t ion of hunter r e p o r t s w i th in a given g r i d coord ina te (36 square mi l e s ) a major f a c t o r i n f l u - encing ind ica t ed c r i p p l i n g l o s s , repor ted c r i p p l i n g would progress ive ly inc rease and show t h e same when p l o t t e d .

Approximately 14% of t h e g r i d coord ina tes sampled from 1968 and 1969 ques t ionna i r e d a t a , show dup l i ca t ion from one period t o the nex t . How- e v e r , when cons ider ing dup l i ca t ion of r e p o r t s w i th in a g r i d o r township, you must cons ider t he v a s t a r e a f o r dup l i ca t ion occurrence a s we l l a s vege ta t ive cover f a c t o r s .

It would seem l i k e l y t h a t dup l i ca t ion too , i s a func t ion of hunt ing pressure . However, dup l i ca t ion o f wounded dee r s i g h t i n g would p ~ s s i b l y be more f requent than d u p l i c a t i o n of dead dee r seen , depending on how many d i e a s a r e s u l t o f wounding, bu t when p l o t t e d s e p a r a t e both d i s p l a y t h e same r e l a t i o n s h i p with ha rves t .

Severa l d ive r s ions from the ha rves t - c r ipp l ing r e l a t i o n s h i p were noted , but an i n t e r e s t i n g one was noted i n per iod 7 o r t h e fou r th weekend i n 1969 and 1970. I n t hese in s t ances ha rves t i s l e s s than period 6 (week days) bu t c r i p p l i n g l o s s a s repor ted goes up from period 6. This perhaps sugges ts a l a g i n r e p o r t i n g o r a tendency toward c a r e l e s s , l a s t chance shoot ing toward the end of t he deer season which would inc rease c r i p p l i n g l o s s .

* Period 1 = opening weekend, per iod 2 = Monday-Friday, per iod 3 = nex t Saturday, Sunday, e t c .

1908 Questionnaire Data

Ynrvest and Wounded and Dcad Deer by Period in Season

- - - - - - = lhrves t = Wounded and Dcad

Combined

- -.-

1969 Questionnaire Data

liarvest and Wounded and Dead Deer by Period in Season

-,,--- = Harvest = !)cad and Wounded

Combined

Period -

1970 Questionnaire Data

Harvest and Wounded and Dead Deer by Period in Season

700-

6 00'

500-

Goo-

300-

100

" '

t 98s \ \

% 5

' \ \

------- = Harvest \ \ = Wounded and Dead \ Combined \

\614 \ I I I \ \ I \ I F, 476 \ I \ \

/ \ / \

\ / \ \ 405 r. \

\ I ' / \

I 'v 374 \ \ I

\ \ I

\ \

I I , 335 I I i I

7 I I I I \ 1

1 \ 235 1 I ,Hh.

L0 . I \ 217

I J 217 Al6. i

f

'\ I /

/6' d I--- 5 2 5 5 d Z

0 c 1 I I

1 I

7 I

3 rt I 1 I 5 6 7 8 9

QUESTIONNAIRE DATA - WOUNDED AND DEAD DEER SEEN

W. & D. & Tota l Wounded & Dead & % of Harvest Harvest

Year Harvest % Inc rease % Inc rease W . D. Tota l Inc rease

The above t a b l e a l s o sugges ts a r e l a t i o n s h i p of c r i p p l i n g l o s s with ha rves t i nc rease . Generally speaking, t h e repor ted dead deer increased more s i g n i f i c a n t l y wi th ha rves t i nc rease than d id wounded deer . A 16.1% inc rease i n ha rves t (1970) r e s u l t e d i n 30.8% more dead dee r r epo r t ed , o r 19.6% minimum l o s s above ha rves t . With the assumption t h a t a wounded dee r w i l l n o t su rv ive , a l o s s of 33.8% o r 1,300 deer a r e l o s t t o a t t a i n a ha rves t o f 3,857 dee r . P r e t t y s t agge r ing f i g u r e s , bu t worthy f o r thought , e s p e c i a l l y when one cons iders t h e p o s s i b i l i t y e x i s t s t h a t on ly a minor f r a c t i o n of the wounded and dead deer a r e r epo r t ed .

The assumption used f o r the above eva lua t ions is centered a t the r e l a t i o n s h i p with ha rves t and c r i p p l i n g , i . e . , t he c o r r e l a t i o n makes the c r i p p l i n g l o s s d a t a v a l i d .

An underlying purpose f o r a l l t h e foregoing fawn s u r v i v a l d a t a is t o be ab l e t o make a s t a b a t determining a recru i tment r a t e f o r t h e breeding populat ion and a t the same time eva lua t e the a c t u a l populat ion t rend .

A key o b j e c t i v e of t h e Ruby-Butte deer s tudy was t o analyze age d a t a obta ined through mandatory hunter check s t a t i o n s and from trapped deer . The too th e rup t ion and wear method was used t o determine age and a l l personnel were t r a i n e d t o pin-point age by year wi th t r a i n i n g r e fe rence t o a known-age jaw c o l l e c t i o n . Age d a t a from harvested deer was obtained from two sources. The f i r s t source came from t h e t r a ined check s t a t i o n a t t e n d a n t . The second age source came from t h e a c t u a l jaw taken by personnel inexperienced a t aging and ages were determined l a t e r a t a jaw aging bee made up of e+ight t o t e n managers. It was f e l t t h a t t h e jaw i n hand method was the most accu ra t e i n f u l l r e a l i z a t i o n of cons tan t e r r o r f a c t o r s .

Age d a t a from 1969 and 1970 a r e compared wi th t rapping d a t a f o r 1970 and 1971 on t h e a t t ached Table 111. The percentages by age c l a s s a r e i n f a c t comparable with few except ions , one being the 1970-71 two-year-old c l a s s . This i s n o t explained a t t h i s po in t . I n genera l terms, percentage age c l a s s diminishes with each yea r of age and t h i s po in ts ou t a v a i l a b i l i t y by age c l a s s and a law of diminishing r e t u r n s with each progress ive year f o r any age c l a s s of dee r . However, t o proper ly eva lua t e herd composition from age d a t a , t h e assumption t h a t ha rves t i s no t s i g n i f i c a n t l y e f f e c t i n g t h e populat ion, must be met. Also a de te rmina t ion must be made with regard f o r t h e v a l i d i t y of t he age sample - i s t he hunter a c t u a l l y randomly sampling?

Age data for 1968, 1969 and 1970 along with sample size is shown in Table IX (all harvest age data). Sample size appears to be nearly as representative as harvest.

Table IX

Age Composition - Harvested Deer Male and Female

Age 1969 19 70 1971 Class No. % No. % No. %

Fawns Yrl. 2 3 4 5 6 7 8 9 lo+

Totals 2,291 100.0 2,782 100.0 3,385 100.0

RUBY-BUTTE AGE DATA - TABLE I11

1.5 2.5 3.5 4 .5 5.5 6 .5 7.5 8.5

1970 Age Data - Harvest

(Jaw Bee) Total Bucks & Does 3 19 % of Total 33.9

1971 Age Data - Trapping Total Bucks & Does 116 % of Total 31.6

1970 Age Data - Harvest (Questionnaire) Total Bucks & Does 1,043

% of Total 34.4

1969 Age Data - Harvest W F-

(Jaw Bee) Total bucks & Does 184 % of Total 37.6

1970 Age Data - Trapping Total Bucks & Does 130 7 5 44 40 3 0 26 2 4 29 % of Total 30.7 17.7 10.4 9.4 7.1 6 .1 5.7 6.8

1969 Age Data - Harvest (Questionnaire) Total bucks & Does 855 6 03 434 259 130 7 9 4 1 3 7

% of Total 34.5 24.2 17.4 10.5 5.4 3.2 1.6 1.5

Data a r e compiled below f o r tagged deer r e tu rns .

Table I V

Marked Deer Returns

Hunt ing Total Year Re turned Total Seasons Tagged 1968 % 1969 ' % 1970 % Return - - - - - -

Totals 1,984 111 5.5 92 6.7 50 8.7 253 12.7

The r a t e of harves t indica ted by re tu rns is low, from 8.8% i n 1968 t o 7.2% i n 1969 and 8.7% i n 1970. The combined harvest of a l l tagged deer r e tu rns i s only 12.7%.

After examination of tagged deer r e tu rns , one may conclude t h a t harvest i s not s i g n i f i c a n t l y a f f e c t i n g the deer herd. Sample s i z e s f o r age information could i n f a c t be a graphic cross s e c t i s n of t h e herd with unevalu- ated e r r o r from one age c l a s s t o the next. The s ign i f i cance of t h a t e r r o r would diminish with each progressive o lder c l a s s . I n the near fu tu re our Department expects t o evaluate cementum layers from i n c i s o r s co l l ec ted during the 1970 and 1971 hunts t o f ind t h i s e r r o r .

A t t h i s point i t appears t h a t age da ta could well be a t r u e p r o f i l e of the herd ' s composition and a trend l i n e fo r the breeding population could be drawn. This method of evaluat ing pqpulation t rends with age da ta i s o ld , but of ten i t takes the back s e a t a s a management t o o l because i t i s misunder- stood .

I n the following paragraph an attempt w i l l be made t o explain e s t ab l i sh ing a trend l i n e f o r the breeding population.

~awn/doe r a t i o s from a given deer herd would be adversely e f fec ted from one year t o the next by high o r low percentage of nonbreeding does (year l ings and 2-year o l d s ) . The su rv iva l of a fawn c l a s s t o breeding age (mainly the 2-year old^) can and w i l l f l u c t u a t e regardless of t o t a l fawn drop o r production. Then a c t u a l fawn su rv iva l w i l l not show up a s a part: o f the breeding population u n t i l i t e n t e r s harvest and has i t s impact on the breed- ing population, i . e . , recrui tment . A high percentage of the breeding popula- t ion should c o p s i s t of 24 through 54 year o lds based on a successive reduction i n numbers with each year of age. Past s t u d i e s on t h i s herd ind ica te about a s i x year turnover r a t e i n the population, weighted heavier agains t bucks. Dis t r ibu t ion of deer ages a l s o demonstrates t h i s same turnover r a t e .