Michael A. Spindler, Orville H. Huntington and Colin B. Brown

Koyukuk/Nowitna National Wildlife Refuge (NWR), PO Box 287, Galena, AK. 99741

Abstract: We compared the effect of using two different aircraft types, Maule M-7 and Piper PA-18 Super Cub, on late-winter moose counts in a 70 mi² area near Galena, Alaska in March 1998. The survey followed standardized fall moose trend count procedures with special attempts to confine sources of variation in survey results solely to aircraft type. In addition to known weight and balance advantages, we determined that for moose surveys the Maule was superior in comfort and efficiency, comparable in operating cost, and produced less pilot and observer fatigue than the Super Cub. The same observer and pilot team counted significantly greater numbers of total moose (28.5%) and adult moose (35.3%) with the Maule compared to the Super Cub. The large window area of the Maule provides potentially greater visibility than the Super Cub and could help biologists obtain more accurate estimates of moose and probably other big game. The Maule will have immediate benefits where historical comparisons are not necessary or where there is no existing long-term data base. However, besides safety, cost, and efficiency, managers and biologists will need to consider the scientific implications of replacing Super Cubs with another aircraft type, especially where retrospective comparisons of current data with historical databases are necessary. We discuss possible sample designs to obtain a Maule-Super Cub correction factor for moose.

Introduction: In November 1997 the U.S. Fish and Wildlife Service assigned a Maule (M-7) aircraft to Koyukuk/Nowitna National Wildlife Refuge (KNNWR) as a replacement for one Super Cub (PA-18) aircraft. The Maule was purchased as part of a regional program to test other types of light aircraft to determine their suitability for wildlife survey, law enforcement, and logistics. The utility of the aging Super Cub fleet was questioned in 1994 when the Dept. of the Interior (DOI) reviewed it’s waiver that allows agency pilots to fly the Super Cub at weights up to 10% (175 lbs.) in excess of the certificated maximum gross weight of 1750 lbs. Without the waiver for the higher weight, the Super Cub would be effective only for full-fuel operations with the pilot as the sole occupant. Two-person operations under 1750 lbs. would require that weight/fuel be reduced to levels that limit viable working range without refueling to an area within a 1 hour flight from the base. Further, in early 1998 the FAA reviewed the DOI practice of allowing overgross operations of the Super Cub, and the fleet was grounded for a week until field inspections could assure that no damages resulted from overgross operations. As of March 1998, the DOI Super Cubs could be flown at a weight not to exceed 1750 lbs., so the need to evaluate proposed Super Cub replacement aircraft was urgent. DOI selected two and that required slightly more time to determine and become familiar with SU boundaries; and (3) the Maule detecteaircraft types with performance and observation capabilities similar to the Super Cub for use in aerial survey, patrol and logistics involving short field take-offs and landings. Galena was chosen as a site to permanently station the first Maule (M-7) in the OAS fleet. Another aircraft type, the Bellanca Scout, was assigned to National Park Service, Kotzebue for similar testing.

Methods: To monitor abundance of moose, 19 trend count areas (50-80 mi²) were defined for periodic early winter aerial surveys in accordance with the KNNWR Wildlife Inventory (USFWS 1992). Each of these trend areas consists of 5-7 sample units (SU’s) with boundaries that can be conveniently observed while in flight. Each SU is 9-14 mi², an area that can usually be surveyed in about an hour. For this comparison study we selected a typical trend area-sized (70 mi² ) sample consisting of six SU’s near Galena that were anticipated to be of average moose density (based on previous surveys). We followed the standardized aerial moose survey technique described by Gasaway et al. (1986) that has been used by the USFWS and ADFG’s since 1980 (Osborne 1995, Spindler 1995, Huntington and Spindler 1997). After the boundaries of each SU were flown, the aircraft traversed each SU at 60-70 mph with a grid of transects spaced about 0.25 mile apart. Areas with moose or suspected moose were circled to classify and search for more moose.For the comparisons in this study we sought to confine sources of variation in survey results solely to aircraft type. Special effort was made to keep the flight pattern and survey intensity similar between the two aircraft. To simulate Cub-like tandem seating in the Maule, the observer sat in he rear seat, behind the pilot, and the right front seat was removed. The same pilot and observer flew all surveys. Pilot Colin Brown has considerable experience (>20 years) piloting Super Cub aircraft for moose surveys in the Galena area, and has the most experience in Maule aircraft of any Alaska DOI pilots. Observer Orville Huntington is an experienced aerial moose survey observer. Each SU was surveyed the same day with each aircraft. On March 4 the crew used the Super Cub to survey units 27 and 28 in the morning. The crew returned in the afternoon to survey the same units with the Maule. The next day, March 5, the crew first surveyed the pair of SUs (158 and 160) with the Maule, followed by the Super Cb. On March 6, SU’s 3 and 4 were surveyed first with the Maule and then with the Super Cub. On the final day, the aircraft type to be used first was drawn randomly so that no type had an artificial advantage related to time of day. Differences in moose counts were tested with the Wilcoxon signed ranks test for paired samples, and correlations were examined with Pearson’s Rank correlation (Zar 1974, SPSS 1997). Differences were considered significant if p < 0.05.

Results: Late winter Moose Count. Significantly more total moose (28.5%) and adult moose (35.3%) were counted with the Maule compared to the Super Cub (Table 1, p=0.027 and p=0.043, respectively). We found no statistically significant differences for yearlings or calves (p=0.176 and p=1.0, respectively). Survey efforts were similar, with 289 minutes in the Super Cub and 312 minutes in the Maule (p =0.066). The Maule flew 8% longer than the Cub for three reasons: (1) at first the pilot’s turns at transect ends had a wider radius and more maneuvering was required to maintain the 0.25 mi transect spacing (he later compensated for this with steeper turns); (2) there were two days in which the Maule made the first flight of the day, d more moose, therefore more circling was required to classify these moose. Total survey time, however, was not correlated to any of the moose count variables obtained by either the Maule or Super Cub (p > 0.437).

Total moose seen per minute of survey time in the Maule was 19.0% greater than the Super Cub, but this was not significant (p=0.116). Likewise, an age ratio calculated from the count data showed a non-significant difference in favor of the Maule. Percent calves, probably the only way to present age ratio in late winter moose surveys, was 19.8% higher in the Maule than the Cub (Table 1, p=0.345). Calculated ratios in fall data, such as calves/100 cows and bulls/100 cows, are usually comparable even if survey area size or SU composition changes (Osborne 1995). Prior to this study we did not expect great differences in moose counts and percent young due to aircraft type and we hoped that the age ratios would be comparable even if total counts, and counts by age class were not. Both the pilot and observer believed they saw more moose from the Maule compared to the Super Cub because of it’s larger window area and less fatiguing design (see discussion on pilot and observer considerations, below).

Cost: The tests in this study required 5.2 hours in the Maule and 5.1 hours in the Super Cub. light time costs were $452 for the Maule and $469 in the Super Cub.

Fuel consumption for these flight times was greater in the Maule: 52 gallons vs. 36 gallons in the Cub. Fuel costs were correspondingly greater for the Maule, $156 vs. $108, respectively. Total costs, including fuel and flight time, were $608 and $577. It should be noted that the fuel consumption differences will likely decrease for more distant survey areas due to the faster commute time of the Maule. Also, greater productivity of the Maule will actually result in a decrease in total flight time and fuel costs relative to the Cub.

Discussion: The ability of the Maule to obtain moose counts that exceeded counts made by the Super Cub, combined with favorable safety, economic performance, and versatility, make the Maule an attractive choice for replacing the Super Cub. The greater number of moose observed per minute in the Maule suggested that the crew may have been more efficient in the Maule. Substantial differences in counts observed between the two aircraft in this preliminary study, however, also suggest that a change to a different moose survey aircraft may complicate retrospective comparisons with historical data from the annual moose trend survey areas. These consequences may not be as significant for the 5-10 year interval moose population estimation surveys because a sightability correction factor (SCF) sub-plot is sampled for each SU (Gasaway et al. 1986, Huntington in prep.). To address this need in the annual trend counts, the sightability correction procedure could be added to each trend SU that is surveyed. Alternatively, a paired sample design as employed for this comparison could be planned in fall 1998 to obtain a Maule-Super Cub correction factor. If needed, the latter option could possibly be applied to the existing database of 17 years of Super Cub-based observations.

Timing: early winter vs. late winter moose counts. The count results obtained in this study in late winter may not accurately reflect the pattern that may be observed in early winter, when moose surveys are usually conducted. Gasaway et al. (1986) reported that moose sightability is much greater in early winter because moose form larger groups and prefer vegetation with low, open canopies. Conversely, lower sightability in March is typical because moose often remain in spruce forest for thermal, energetic, and predator-avoidance reasons that may be related to less snow depth beneath the canopy. Indeed, a comparison of our Super Cub counts in 4 of the 6 SU’s sampled in March 1998 showed 44% fewer moose than the same area in November 1997 (Appendix 1).

Time of day. During mid-day in March the survey crew observed moose moving out of timbered areas into the more open areas. If this movement had biased results in the aircraft type comparisons, it would have biased them in favor of the Super Cub, because in 2 of the 3 days the Cub was used in the afternoon. Perhaps with the greater window area of the Maule, the crew was able to do a better job of spotting moose in the spruce cover in the morning than from the Cub.

Sightability of other species: The patterns observed in this preliminary study may not necessarily be similar for other pilots, observers, and wildlife species. For example, a July 1997 preliminary comparison of aerial goose transect data with the same two aircraft types yielded Maule counts of white-fronted and Canada geese that were 46% and 59% less, respectively, than the Super Cub counts (Appendix 2). These were preliminary observations with a limited sample size and further testing is needed. We anticipate greater difficulty in testing aircraft type effect on migratory birds surveys because ducks and geese are more difficult to detect and identify from a moving airplane relative to moose. Hodges et al. (1994) documented a 25% mean increase in estimated total ducks when the USFWS changed from a Cessna to a Turbine Beaver in 1977. Hodges et al. (1994) attributed significant increases in the estimates for 7 of 11 duck species to the change in aircraft type. The same study did not show significant differences in migratory bird cunts due to different observers as long as they were experienced and well-trained.

Moose survey observer considerations: Observer Huntington reported that forward, downward, and left side visibility was greater in the Maule than the Cub. He reported the comfort level in the Maule was superior, because of greater leg room, elbow room, and cabin warmth. In the Super Cub, when the observer had to cover the pilot’s assigned side (usually left), the observer had to compromise observations on his side (usually right) during turns. This did not happen in the Maule because of greater downward visibility in a turn. The visibility through the observer’s windows in the Maule is so good that the observer can concentrate on seeing animals and does not have to be conscious of moving his/her head to a place where the view is better (as in the Cub, especially when wearing a helmet). In the Maule, by sitting slightly right of center, the observer can: (1) look almost straight down with minimal head or eye movement; (2) cover transect lines on the right side of the plane without moving; and (3) cover the pilot’s side by glancing out the left window and occasionally looking down.

Pilot considerations: Both pilots at KNNWR reported that fatigue was much less in the Maule compared to the Cub, mainly due to increased leg and elbow room, better heat system, and less vibration and noise. Even with a heavy pilot and observer, the Maule can be flown at legal weight on flights up to four hours without refueling. The Maule’s faster cruise speed allows it to commute to survey areas faster than the Super Cub, allowing for increased productivity. For November moose surveys, this translates to one more SU completed per day than the Super Cub. Both pilots reported that the cruise capability of the Maule did not seem to have a related penalty at the slower speeds (60-70 mph) used for surveys. As with any aircraft, once checked out in the Maule, pilots should plan on an additional proficiency-building period of several hours surveying moose SU’s of low density, using slightly faster speed, 65-70 mph. Once experience and confidence are gained, the pilot can then use slower speeds, 60-65 mph, and more turns, if necessary, to survey the more challenging with medium and high moose density SU’s. Both pilots reported having to use steeper turns in the Maule to maintain transect lines with the same 0.25 mile spacing as Cubs, thus requiring more frequent manipulation of the throttle. Spindler reported that after 20 hours of practice in the plane, proficiency improved, but still there was some discomfort associated with greater reliance on throttle and power in steeper turns at slow speeds compared to moose surveys in the Super Cub. Brown reported he was comfortable with the plane after just a few hours of moose surveys. Spindler reported poorer visibility over the nose in the Maule, and suggests that shorter pilots use a 2 inch thick seat cushion to raise their head and improve over-the nose visibility.

Recommendations: 

1. Consult with a biometrician to design a comparison experiment to be conducted during moose surveys in November 1998. The main goal would be to determine if a correction factor can be estimated and used to adjust previous years’ Cub data to allow it to be compared to Maule data. Such a moose survey comparison study could include four possible approaches: (A) Obtain a larger sample using paired surveys in established moose trend areas with thoroughly known historical data (e.g. Nowitna Mouth and Nowitna/Sulatna, Three Day Slough); (B) Conduct sightability correction factor (SCF) sub-plots on all SU’s surveyed for annual moose trend areas; (C) WithVer Hoef’s regression population estimation method, conduct concurrent mini-censuses (with SCF sub-plots) each using Maule and Cub; and (D) Recognize the differences between aircraft types by plotting results separately. Trend lines may have different intercepts but will probably have similar slopes (per Hodges et al. 1996).

2. Consult with a biometrician to help design a similar experiment to be conducted during the July aerial goose transect surveys. This experiment is logistically more difficult because of the long flight times (5-8 hours per survey area), and the impossibility of using the same pilot and observer to concurrently survey the same unit in a day.

3. Encourage similar concurrent tests of moose and swan surveys with the Super Cub and Bellanca Scout assigned to Selawik NWR and NPS, respectively in Kotzebue.

4. After more data are obtained in 1998, thoroughly evaluate the scientific impacts of changing aerial survey aircraft, and consider these impacts before committing to a long-term change of primary survey aircraft on KNNWR. Report these findings to Regional Aviation managers of USFWS and NPS for consideration before making a fleet-wide decision to change.