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Elk behavior in response to human disturbance at Mount St. Helens National Volcanic Monument
Applied Animal Behaviour Science, 29 ( 1991 ) 269-277
269
Elsevier Science Publishers B.V., Amsterdam
Elk behavior in response to human disturbance at Mount St. Helens National Volcanic Monument Brian Czech* College of Forest Resources, University of Washington, Seattle, WA 98195 (U.S.A.)
ABSTRACT Czech, B., 1991. Elk behavior in response to human disturbance at Mount St. Helens National Volcanic Monument. Appl. Anita. Behav. Sci., 29: 269-277. The edge of the Mount St. Helens volcanic blast zone attracts high summer densities of Roosevelt elk (Cervus elaphus roosevelti). Forest Service Road 2560 (a previously existing logging road) was opened to the public in the Clearwater drainage of the blast zone in 1987, and elk use was monitored. During that year, elk avoided a 500 m corridor centered on the road, as well as several sections in the study area where the influence of the road was prominent. This avoidance was probably a learned behavioral response to public use of Forest Service Road 2560 but might also reflect a higher frequency of flight reactions to traffic. Maximum herd size also decreased in 1987 as a response to frequent passive harassment by humans on Forest Service Road 2560 (such as getting out of cars), as large herds were more likely to be seen and were more vulnerable to initiation of a flight reaction. Logging also produced by-products of human activity that constituted passive harassment even when humans were temporarily absent (e.g. foreign noises and materials). Elk tolerance of timber operations was correlated positively with proximity to hiding cover. A high level of habituation by elk to disturbance in the Clearwater blast zone will probably be preceded by the hiding cover stage of plant succession.
INTRODUCTION
After the eruption of Mount St. Helens on 18 May 1980 and the subsequent creation of the National Volcanic Monument, visitor use increased dramatically. It soon became apparent that the traditional route to Mount St. Helens (U.S. Forest Service Road 99) would be insufficient to handle the increased flow of traffic. The Forest Service decided to widen Road 99, with construction beginning in 1987. Until its completion, Forest Service Road 2560 (hereafter "2560"), a logging road not previously available to the public, would be opened to provide access to the mountain. The Washington Department of Wildlife objected to this decision. They *Present address: Recreation and Wildlife Department, San Carlos Apache Tribe, P.O. Box 97, San Carlos, AZ 85550, U.S.A.
270
B. CZECH
felt that to open 2560 would have a negative impact on the herd of Roosevelt elk (Cervus elaphus roosevelti) in the Clearwater drainage of the volcanic blast zone. Previous elk studies had shown that roads, or disturbance which accompanies roads, can have an impact upon elk use of adjacent areas (Thiessen, 1976; Hershey and Leege, 1976; Perry and Overly, 1976; Lyon, 1979; Rost and Bailey, 1979; Lyon and Jensen, 1980; Irwin and Peek, 1983; Grover and Thompson, 1986). This prompted the Forest Service to initiate a study to determine the impact on elk of opening the 2560 to recreational traffic within the context of pre-existing and simultaneous non-recreational disturbances. The results of the study would be used in formulating future management plans for the road. S T U D Y AREA
Most of the Clearwater drainage was devastated by the 1980 eruption of Mount St. Helens. It is now in the early stages of reforestation and fits the United States Department of Agriculture (1984) definition of transitory range. Elk have used this range heavily in recent years. The portion of the Clearwater drainage undamaged by the eruption is dominated by mature Pacific silver fir (Abies amabilis), and 20-30% of this area consists of recent clearcuts. Elevations in the study area range from ~ 550 to 1400 m above sea level. Slopes range from 0 to 90 ° cliffs, averaging ~ 35 ° on the sides of the Clearwater Valley. The 2560 leads from Road 25 high on the east side of the Clearwater Valley to Road 99 at the head of Bean Creek (the adjacent drainage to the west; Fig. 1. ). About 7 km of the 2560 is situated between the edge of the blast zone and the Clearwater Valley floor, which contains very little hiding cover. This promotes the opinion that elk in the study area are subject to significant impacts from heavy recreational traffic. ANIMALS, M A T E R I A L S A N D M E T H O D S
Four elk were monitored by radio telemetry from August to November 1986. The same 4 animals and 2 other elk were monitored during the same period of 1987. Two additional elk were equipped with visual collars in 1987. All collared animals were cows. The radio-collared elk were located regularly and at all hours by triangulation, using portable equipment from the road system in the study area. For most data analyses, only radio bearings which created a polygon of <0.33 km 2 were considered. Exceptions occurred for parameters that became obvious despite larger polygons (e.g. if all bearings were westerly from the Clearwater blast zone edge, then the animal was classified as being in the blast
HUMAN DISTURBANCEAND ELK BEHAVIORAT MT. ST. HELENS
271
~Qend: -----m m
blast zone edge primary road
..........
secondary creek
. . . . ""
road
I
o
1
•. - < "
+,,.1".*+'
"h
tl~,
)
'\" t
( ',
3
Pal'ldl~,.~
;',
.
,.
.,j
I
t
FIIIO
-,
//"-
,,.
,
.~ /"
Fig. |. S t u d y area.
zone). Notes were taken when elk were sighted and these included behavioral response to activity on the 2560. Chi-square goodness of fit tests (with 95% confidence ) were used to quantify elk use changes effected after the 2560 was opened to the public. RESULTS AND DISCUSSION
Social structure
In 1986, ~ 175 elk used the study area. Most belonged to one of four bands, (1) Paradise Falls, (2) northern, (3) southern, and (4) Bean Creek. The Paradise Falls band was the primary user of the Clearwater blast zone and
272
B. CZECH
consisted of ~ 30 elk. The northern band, consisting of ~ 55 elk, was a frequent user of the Clearwater blast zone, and the other two bands used it intermittently. The largest herds seen in the blast zone, resulting from intermingling of the bands, contained > 100 elk. These herds were sighted in the northern portion of the study area during 1986. In 1987, the same four main bands used the study area. However, the northern band consisted of ~ 25 fewer elk. The "missing" component did not include any radio-collared animals but was believed to have centered its activities in the northeastern portion of the study area, avoiding the Clearwater blast zone during daylight. Elk sign indicated that these "missing" elk did frequent the northern portion of the valley floor nocturnally. After the logging road 2560 was opened to the public, large herds ( > 50 elk) were seldom seen in the northern portion of the Clearwater blast zone. This is interpreted to represent a response by elk to human disturbance. Large herds of elk on the Clearwater Valley floor are more visible from the 2560 than are small herds. Thus, people driving along the 2560 are more likely to stop to view large herds. This type of "passive harassment" (Horejsi, 1976) almost always caused increased alertness and often resulted in flight. Larger herds also were more likely to contain highly vigilant animals that were more responsive to disturbance. On the Clearwater Valley floor, the response to disturbance often developed from a gradual spread of increased alertness to a decision for flight made by one animal. Almost always, flight of the entire herd followed. Whatever the disturbance level, smaller herds were less likely to contain an animal that would break for cover. Reactions to non-recreational disturbance In the 1986 study season, elk avoided a logging site that was located in the central portion of the valley floor. Logging operations had begun at this site in the spring of 1986. In addition to the associated traffic, logging activity included other disturbances such as the presence of humans separate from vehicles, loud noise, and highly visible equipment operation. An example from 1987 indicated that elk may become less wary of logging operations under certain circumstances. A band of elk was observed feeding in the Clearwater blast zone within 100 m of an active yarding operation and within 175 m of falling operations. The log-yarding tower and loader were working near the edge of the blast zone while timber was being felled along the very edge, ~ 75 m further away from the elk than the yarding site. The outstanding difference between this 1987 situation and the 1986 salvage site on the valley floor is the proximity to hiding cover. When the feeding elk in the 1987 example were observed, they were above the logging activities and the blast zone edge was only 30 m above them. After feeding for ~ 30 min,
H U M A N D I S T U R B A N C E A N D E L K B E H A V I O R A T M T . ST. H E L E N S
273
they calmly re-entered the forest and bedded nearby. Near the 1986 salvage sale, no extensive cover existed. Two observations indicated that passive harassment owing to humans can occur without the actual presence of humans. The Paradise Falls band was observed to "spook" early one morning from the area of the valley floor salvage sale, although humans had not yet arrived at the logging site. A loud voice, however, was heard from the yarding area. It was later discovered that the operator occasionally left a two-way radio switched on in the cab of a loader. The volume was high so that transmissions could be heard above the noise of yarding operations, and radio traffic by loggers usually began earlier in the morning than logging. On another occasion in late summer, the Paradise Falls band was spooked from the Clearwater Creek area for unknown reasons. When the band was intercepted near the blast zone edge, a 4-point bull was seen with a piece ( ~ 1 m 2) of black plastic entangled in his antlers. Plastic had been used to cover logging debris on the valley floor before the piles were to be burned. Apparently the bull had been sparring with inanimate objects and the plastic had become caught in his antlers, frightening him to flight. The response must have spread through the whole band.
Avoidance of the 2560 When the 2560 was opened to the public in 1987, the collective elk herd responded by avoiding a corridor centered on the 2560. Figure 2 uses 250-m increments to demonstrate this avoidance. Typically, when elk were encountered by study personnel, their reaction was flight. When they were on the road itself, flight was almost always toward the blast zone edge and the hiding cover beyond. When elk were close to, but below (west of), the 2560 when a vehicle approached, response varied from flight straight to Clearwater Creek riparian cover, to a wide circling of the vehicle and subsequent flight to the blast zone LOCATIONS IJ~M~ON TOTAI.rm 1908 - 21 lgl7 - 27
k~lt~
15
tO
5
0
0--2S0
500-750
750~1000
01STAN~ FROI4Z560 (NETF.RS) Fig. 2. Distribution of elk locations among Road 2560 distance categories, 1986 and 1987.
274
B. CZECH
edge with crossing of the 2560 more than 1 km from the vehicle. Uncertainty often seemed to accompany the latter method of escape, because, in some instances, elk stopped several hundred meters from the 2560 and watched the vehicle until it moved off. Removal of the vehicle sometimes resulted in the elk settling down, but was often followed by the delayed response of further flight. In almost all cases except straight flight, elk veered south in their escape attempts. By doing so, they would eventually reach the blast zone edge without having to cross the 2560 (Fig. 1 ). Also, there is a considerable amount of hiding cover within the valley floor in its mid-southern reaches. The spur roads of the 2560 were always closed to the public but were used by elk study personnel. Violations of the closures by the public were not uncommon. When elk encountered humans on the spurs in the valley floor, the elk usually fled to the blast zone edge, especially when humans were separated from their vehicle. Elk response to individual encounters with vehicles or with humans on foot did not seem to differ between study seasons. Therefore, the avoidance of the 2560 in 1987 should be viewed partially as an effect of an increased number of such encounters. It would also seem that this frequency became high enough to result in active avoidance of the 2560 area during the initial opening period covered by the study.
Spatial preference Herd response to the opening of the 2560 was an abandonment of the northernmost portion of the study area (except nocturnally by the unmarked splinter group from the northern band). This is made apparent by a comparison of distribution maps for 1986 and 1987, and especially of Animals 1 (Fig. 3 ) and 3 (Fig. 4). These animals represent the Paradise Falls band and the northern band, respectively. Subdividing the study area into its 15 major legal sections (all sections which contain a portion of the Clearwater blast zone or standing timber immediately east of the Clearwater blast zone) and testing the 1987 locations for goodness of fit (to an expected distribution derived from 1986 use patterns) supports this conclusion. Elk use of approximately 4 miles 2 of the northern portion of the study area was affected. In 1986, ~ 80 elk (a congregation of the Paradise Falls and northern bands ) used this area for several weeks during early fall. They were observed emerging from the timber northeast of the Clearwater Creek bridge on the 2560 numerous times. Sometimes they fed on their way down the slope, but often they went immediately to the northern portion of the valley floor to graze on lush stands offireweed (Epilobium angustifolium). On the few occasions that vehicular traffic and this downslope movement of elk were observed simultaneously, the downslope movement of elk was interrupted, and they did not reach the valley floor before darkness.
275
H U M A N DISTURBANCE A N D ELK BEHAVIOR AT MT. ST. HELENS
j
1986
1987
Fig. 3. Locations of Animal 1, 1986 and 1987.
1986
Fig. 4. Locations of Animal 3, 1986 and 1987.
1987
276
a. CZECH
Elk have limited access to the valley floor from the slope because of a highcut bank above the 2560. The few sites manageable for elk are very narrow. Therefore, elk usually go single file when crossing the 2560 in this area. A few times the herd was split up by activity on the 2560, with one portion responding by flight toward Clearwater Creek and southward away from the bridge area, and the other portion by flight back upslope to the edge o f the blast zone. During the s u m m e r o f 1987, > 60 000 vehicles used the 2560 compared with 2200 in 1986. The peak hour for traffic was 1 7 : 0 0 - 1 8 : 0 0 h ( 1 3 : 0 0 14:00 h in 1986 ), and a steady stream o f vehicles from 15 : 00 h until darkness was not u n c o m m o n in 1987. Although there are other possible reasons for the a b a n d o n m e n t o f the northern portion in 1987, such as road construction activities ~ 2.5 km northeast of the Clearwater bridge and absence of salvage logging in the central portion of the study area, constant disturbance upon entry to the valley floor is the most likely. CONCLUSION An initial reaction of elk to public travel on the 2560 was expected, The duration of this reaction will be influenced by the elks' association of people and vehicles with undesirable consequences and by plant succession o f the Clearwater blast zone. The study area is open to typical elk hunting seasons in fall, archery and rifle. This will delay habituation o f the elk population to people and vehicles. Eventually, elk would probably habituate seasonally, becoming less reactive to people and vehicles during periods further from hunting seasons. However, rapid growth of Douglas fir (Pseudotsuga menziesii) should provide hiding cover throughout the Clearwater Valley floor before such fine-tuned habituation becomes pronounced.
REFERENCES Grover, K.E. and Thompson, M.J., 1986. Factors influencing spring feeding site selection by elk in the Elkhorn Mountains, Montana. J. Wildl. Manage., 50 (3): 466-470. Hershey, T.L. and Leege, T.A., 1976. Influences of logging on elk on summer range in northcentral Idaho. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 73-80. Horejsi, B., 1976. Some thoughts and observations on harassment and bighorn sheep. In: Proceedings of the Northern Wild Sheep Conference, Jackson, WY, February 1976, pp. 1-12. Irwin, L.L. and Peek, J.M., 1983. Elk habitat use relative to forest succession in Idaho. J. Wildl. Manage., 47 (3): 664-672. Lyon, L.J., 1979. Habitat effectivenessfor elk as influenced by roads and cover. J. For., 77 ( 10): 658-660. Lyon, L.J. and Jensen, C,E., 1980. Management implications of elk and deer use ofclearcuts in Montana. J. Wildl. Manage., 44 (2): 352-362.
HUMAN DISTURBANCE AND ELK BEHAVIOR AT MT. ST. HELENS
277
Perry, C. and Overly, R., 1976. Impact of roads on big game distribution in portions of the Blue Mountains of Washington. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 62-68. Rost, G.R. and Bailey, J.A., 1979. Distribution of mule deer and elk in relation to roads. J. Wildl. Manage., 43 (3): 634-641. Thiessen, J.L., 1976. Some relations of elk to logging, roading and hunting in Idaho's game management unit 39. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 3-5. United States Department of Agriculture, 1984. Range Analysis and Management Handbook. Forest Service Handbook 2209.21.
269
Elsevier Science Publishers B.V., Amsterdam
Elk behavior in response to human disturbance at Mount St. Helens National Volcanic Monument Brian Czech* College of Forest Resources, University of Washington, Seattle, WA 98195 (U.S.A.)
ABSTRACT Czech, B., 1991. Elk behavior in response to human disturbance at Mount St. Helens National Volcanic Monument. Appl. Anita. Behav. Sci., 29: 269-277. The edge of the Mount St. Helens volcanic blast zone attracts high summer densities of Roosevelt elk (Cervus elaphus roosevelti). Forest Service Road 2560 (a previously existing logging road) was opened to the public in the Clearwater drainage of the blast zone in 1987, and elk use was monitored. During that year, elk avoided a 500 m corridor centered on the road, as well as several sections in the study area where the influence of the road was prominent. This avoidance was probably a learned behavioral response to public use of Forest Service Road 2560 but might also reflect a higher frequency of flight reactions to traffic. Maximum herd size also decreased in 1987 as a response to frequent passive harassment by humans on Forest Service Road 2560 (such as getting out of cars), as large herds were more likely to be seen and were more vulnerable to initiation of a flight reaction. Logging also produced by-products of human activity that constituted passive harassment even when humans were temporarily absent (e.g. foreign noises and materials). Elk tolerance of timber operations was correlated positively with proximity to hiding cover. A high level of habituation by elk to disturbance in the Clearwater blast zone will probably be preceded by the hiding cover stage of plant succession.
INTRODUCTION
After the eruption of Mount St. Helens on 18 May 1980 and the subsequent creation of the National Volcanic Monument, visitor use increased dramatically. It soon became apparent that the traditional route to Mount St. Helens (U.S. Forest Service Road 99) would be insufficient to handle the increased flow of traffic. The Forest Service decided to widen Road 99, with construction beginning in 1987. Until its completion, Forest Service Road 2560 (hereafter "2560"), a logging road not previously available to the public, would be opened to provide access to the mountain. The Washington Department of Wildlife objected to this decision. They *Present address: Recreation and Wildlife Department, San Carlos Apache Tribe, P.O. Box 97, San Carlos, AZ 85550, U.S.A.
270
B. CZECH
felt that to open 2560 would have a negative impact on the herd of Roosevelt elk (Cervus elaphus roosevelti) in the Clearwater drainage of the volcanic blast zone. Previous elk studies had shown that roads, or disturbance which accompanies roads, can have an impact upon elk use of adjacent areas (Thiessen, 1976; Hershey and Leege, 1976; Perry and Overly, 1976; Lyon, 1979; Rost and Bailey, 1979; Lyon and Jensen, 1980; Irwin and Peek, 1983; Grover and Thompson, 1986). This prompted the Forest Service to initiate a study to determine the impact on elk of opening the 2560 to recreational traffic within the context of pre-existing and simultaneous non-recreational disturbances. The results of the study would be used in formulating future management plans for the road. S T U D Y AREA
Most of the Clearwater drainage was devastated by the 1980 eruption of Mount St. Helens. It is now in the early stages of reforestation and fits the United States Department of Agriculture (1984) definition of transitory range. Elk have used this range heavily in recent years. The portion of the Clearwater drainage undamaged by the eruption is dominated by mature Pacific silver fir (Abies amabilis), and 20-30% of this area consists of recent clearcuts. Elevations in the study area range from ~ 550 to 1400 m above sea level. Slopes range from 0 to 90 ° cliffs, averaging ~ 35 ° on the sides of the Clearwater Valley. The 2560 leads from Road 25 high on the east side of the Clearwater Valley to Road 99 at the head of Bean Creek (the adjacent drainage to the west; Fig. 1. ). About 7 km of the 2560 is situated between the edge of the blast zone and the Clearwater Valley floor, which contains very little hiding cover. This promotes the opinion that elk in the study area are subject to significant impacts from heavy recreational traffic. ANIMALS, M A T E R I A L S A N D M E T H O D S
Four elk were monitored by radio telemetry from August to November 1986. The same 4 animals and 2 other elk were monitored during the same period of 1987. Two additional elk were equipped with visual collars in 1987. All collared animals were cows. The radio-collared elk were located regularly and at all hours by triangulation, using portable equipment from the road system in the study area. For most data analyses, only radio bearings which created a polygon of <0.33 km 2 were considered. Exceptions occurred for parameters that became obvious despite larger polygons (e.g. if all bearings were westerly from the Clearwater blast zone edge, then the animal was classified as being in the blast
HUMAN DISTURBANCEAND ELK BEHAVIORAT MT. ST. HELENS
271
~Qend: -----m m
blast zone edge primary road
..........
secondary creek
. . . . ""
road
I
o
1
•. - < "
+,,.1".*+'
"h
tl~,
)
'\" t
( ',
3
Pal'ldl~,.~
;',
.
,.
.,j
I
t
FIIIO
-,
//"-
,,.
,
.~ /"
Fig. |. S t u d y area.
zone). Notes were taken when elk were sighted and these included behavioral response to activity on the 2560. Chi-square goodness of fit tests (with 95% confidence ) were used to quantify elk use changes effected after the 2560 was opened to the public. RESULTS AND DISCUSSION
Social structure
In 1986, ~ 175 elk used the study area. Most belonged to one of four bands, (1) Paradise Falls, (2) northern, (3) southern, and (4) Bean Creek. The Paradise Falls band was the primary user of the Clearwater blast zone and
272
B. CZECH
consisted of ~ 30 elk. The northern band, consisting of ~ 55 elk, was a frequent user of the Clearwater blast zone, and the other two bands used it intermittently. The largest herds seen in the blast zone, resulting from intermingling of the bands, contained > 100 elk. These herds were sighted in the northern portion of the study area during 1986. In 1987, the same four main bands used the study area. However, the northern band consisted of ~ 25 fewer elk. The "missing" component did not include any radio-collared animals but was believed to have centered its activities in the northeastern portion of the study area, avoiding the Clearwater blast zone during daylight. Elk sign indicated that these "missing" elk did frequent the northern portion of the valley floor nocturnally. After the logging road 2560 was opened to the public, large herds ( > 50 elk) were seldom seen in the northern portion of the Clearwater blast zone. This is interpreted to represent a response by elk to human disturbance. Large herds of elk on the Clearwater Valley floor are more visible from the 2560 than are small herds. Thus, people driving along the 2560 are more likely to stop to view large herds. This type of "passive harassment" (Horejsi, 1976) almost always caused increased alertness and often resulted in flight. Larger herds also were more likely to contain highly vigilant animals that were more responsive to disturbance. On the Clearwater Valley floor, the response to disturbance often developed from a gradual spread of increased alertness to a decision for flight made by one animal. Almost always, flight of the entire herd followed. Whatever the disturbance level, smaller herds were less likely to contain an animal that would break for cover. Reactions to non-recreational disturbance In the 1986 study season, elk avoided a logging site that was located in the central portion of the valley floor. Logging operations had begun at this site in the spring of 1986. In addition to the associated traffic, logging activity included other disturbances such as the presence of humans separate from vehicles, loud noise, and highly visible equipment operation. An example from 1987 indicated that elk may become less wary of logging operations under certain circumstances. A band of elk was observed feeding in the Clearwater blast zone within 100 m of an active yarding operation and within 175 m of falling operations. The log-yarding tower and loader were working near the edge of the blast zone while timber was being felled along the very edge, ~ 75 m further away from the elk than the yarding site. The outstanding difference between this 1987 situation and the 1986 salvage site on the valley floor is the proximity to hiding cover. When the feeding elk in the 1987 example were observed, they were above the logging activities and the blast zone edge was only 30 m above them. After feeding for ~ 30 min,
H U M A N D I S T U R B A N C E A N D E L K B E H A V I O R A T M T . ST. H E L E N S
273
they calmly re-entered the forest and bedded nearby. Near the 1986 salvage sale, no extensive cover existed. Two observations indicated that passive harassment owing to humans can occur without the actual presence of humans. The Paradise Falls band was observed to "spook" early one morning from the area of the valley floor salvage sale, although humans had not yet arrived at the logging site. A loud voice, however, was heard from the yarding area. It was later discovered that the operator occasionally left a two-way radio switched on in the cab of a loader. The volume was high so that transmissions could be heard above the noise of yarding operations, and radio traffic by loggers usually began earlier in the morning than logging. On another occasion in late summer, the Paradise Falls band was spooked from the Clearwater Creek area for unknown reasons. When the band was intercepted near the blast zone edge, a 4-point bull was seen with a piece ( ~ 1 m 2) of black plastic entangled in his antlers. Plastic had been used to cover logging debris on the valley floor before the piles were to be burned. Apparently the bull had been sparring with inanimate objects and the plastic had become caught in his antlers, frightening him to flight. The response must have spread through the whole band.
Avoidance of the 2560 When the 2560 was opened to the public in 1987, the collective elk herd responded by avoiding a corridor centered on the 2560. Figure 2 uses 250-m increments to demonstrate this avoidance. Typically, when elk were encountered by study personnel, their reaction was flight. When they were on the road itself, flight was almost always toward the blast zone edge and the hiding cover beyond. When elk were close to, but below (west of), the 2560 when a vehicle approached, response varied from flight straight to Clearwater Creek riparian cover, to a wide circling of the vehicle and subsequent flight to the blast zone LOCATIONS IJ~M~ON TOTAI.rm 1908 - 21 lgl7 - 27
k~lt~
15
tO
5
0
0--2S0
500-750
750~1000
01STAN~ FROI4Z560 (NETF.RS) Fig. 2. Distribution of elk locations among Road 2560 distance categories, 1986 and 1987.
274
B. CZECH
edge with crossing of the 2560 more than 1 km from the vehicle. Uncertainty often seemed to accompany the latter method of escape, because, in some instances, elk stopped several hundred meters from the 2560 and watched the vehicle until it moved off. Removal of the vehicle sometimes resulted in the elk settling down, but was often followed by the delayed response of further flight. In almost all cases except straight flight, elk veered south in their escape attempts. By doing so, they would eventually reach the blast zone edge without having to cross the 2560 (Fig. 1 ). Also, there is a considerable amount of hiding cover within the valley floor in its mid-southern reaches. The spur roads of the 2560 were always closed to the public but were used by elk study personnel. Violations of the closures by the public were not uncommon. When elk encountered humans on the spurs in the valley floor, the elk usually fled to the blast zone edge, especially when humans were separated from their vehicle. Elk response to individual encounters with vehicles or with humans on foot did not seem to differ between study seasons. Therefore, the avoidance of the 2560 in 1987 should be viewed partially as an effect of an increased number of such encounters. It would also seem that this frequency became high enough to result in active avoidance of the 2560 area during the initial opening period covered by the study.
Spatial preference Herd response to the opening of the 2560 was an abandonment of the northernmost portion of the study area (except nocturnally by the unmarked splinter group from the northern band). This is made apparent by a comparison of distribution maps for 1986 and 1987, and especially of Animals 1 (Fig. 3 ) and 3 (Fig. 4). These animals represent the Paradise Falls band and the northern band, respectively. Subdividing the study area into its 15 major legal sections (all sections which contain a portion of the Clearwater blast zone or standing timber immediately east of the Clearwater blast zone) and testing the 1987 locations for goodness of fit (to an expected distribution derived from 1986 use patterns) supports this conclusion. Elk use of approximately 4 miles 2 of the northern portion of the study area was affected. In 1986, ~ 80 elk (a congregation of the Paradise Falls and northern bands ) used this area for several weeks during early fall. They were observed emerging from the timber northeast of the Clearwater Creek bridge on the 2560 numerous times. Sometimes they fed on their way down the slope, but often they went immediately to the northern portion of the valley floor to graze on lush stands offireweed (Epilobium angustifolium). On the few occasions that vehicular traffic and this downslope movement of elk were observed simultaneously, the downslope movement of elk was interrupted, and they did not reach the valley floor before darkness.
275
H U M A N DISTURBANCE A N D ELK BEHAVIOR AT MT. ST. HELENS
j
1986
1987
Fig. 3. Locations of Animal 1, 1986 and 1987.
1986
Fig. 4. Locations of Animal 3, 1986 and 1987.
1987
276
a. CZECH
Elk have limited access to the valley floor from the slope because of a highcut bank above the 2560. The few sites manageable for elk are very narrow. Therefore, elk usually go single file when crossing the 2560 in this area. A few times the herd was split up by activity on the 2560, with one portion responding by flight toward Clearwater Creek and southward away from the bridge area, and the other portion by flight back upslope to the edge o f the blast zone. During the s u m m e r o f 1987, > 60 000 vehicles used the 2560 compared with 2200 in 1986. The peak hour for traffic was 1 7 : 0 0 - 1 8 : 0 0 h ( 1 3 : 0 0 14:00 h in 1986 ), and a steady stream o f vehicles from 15 : 00 h until darkness was not u n c o m m o n in 1987. Although there are other possible reasons for the a b a n d o n m e n t o f the northern portion in 1987, such as road construction activities ~ 2.5 km northeast of the Clearwater bridge and absence of salvage logging in the central portion of the study area, constant disturbance upon entry to the valley floor is the most likely. CONCLUSION An initial reaction of elk to public travel on the 2560 was expected, The duration of this reaction will be influenced by the elks' association of people and vehicles with undesirable consequences and by plant succession o f the Clearwater blast zone. The study area is open to typical elk hunting seasons in fall, archery and rifle. This will delay habituation o f the elk population to people and vehicles. Eventually, elk would probably habituate seasonally, becoming less reactive to people and vehicles during periods further from hunting seasons. However, rapid growth of Douglas fir (Pseudotsuga menziesii) should provide hiding cover throughout the Clearwater Valley floor before such fine-tuned habituation becomes pronounced.
REFERENCES Grover, K.E. and Thompson, M.J., 1986. Factors influencing spring feeding site selection by elk in the Elkhorn Mountains, Montana. J. Wildl. Manage., 50 (3): 466-470. Hershey, T.L. and Leege, T.A., 1976. Influences of logging on elk on summer range in northcentral Idaho. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 73-80. Horejsi, B., 1976. Some thoughts and observations on harassment and bighorn sheep. In: Proceedings of the Northern Wild Sheep Conference, Jackson, WY, February 1976, pp. 1-12. Irwin, L.L. and Peek, J.M., 1983. Elk habitat use relative to forest succession in Idaho. J. Wildl. Manage., 47 (3): 664-672. Lyon, L.J., 1979. Habitat effectivenessfor elk as influenced by roads and cover. J. For., 77 ( 10): 658-660. Lyon, L.J. and Jensen, C,E., 1980. Management implications of elk and deer use ofclearcuts in Montana. J. Wildl. Manage., 44 (2): 352-362.
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Perry, C. and Overly, R., 1976. Impact of roads on big game distribution in portions of the Blue Mountains of Washington. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 62-68. Rost, G.R. and Bailey, J.A., 1979. Distribution of mule deer and elk in relation to roads. J. Wildl. Manage., 43 (3): 634-641. Thiessen, J.L., 1976. Some relations of elk to logging, roading and hunting in Idaho's game management unit 39. In: S.R. Heib (Editor), Proceedings of the Elk-Logging-Roads Symposium, University of Idaho, Moscow, ID, pp. 3-5. United States Department of Agriculture, 1984. Range Analysis and Management Handbook. Forest Service Handbook 2209.21.