During winter 1996-1997 and summer 1997, I studied bird assemblages along a vegetation gradient in desert grasslands of southeast Arizona and southwest New Mexico. A gradient of increasing woody cover and decreasing grass cover best described the variance in vegetation characteristics among sites. At larger scales of observation, I found woody plant characteristics had a large effect on the presence and distribution of individual species and assemblages. At finer scales of analysis, I found a greater proportion of relationships between birds and particular plant species. Bird species richness was positively related to shrub species richness during winter. I observed greater between season shifts in bird species richness among sites with >1.0% woody cover. Total bird abundance varied little between seasons except at sites with 1.0% woody cover. Woody plant levels below 10% and 20% are likely to increase populations of plains and semidesert grassland bird communities respectively.

I studied bat use of 3 isolated water developments on the Cabeza Prieta National Wildlife Refuge in southwestern Arizona between May 1995 and August 1997. I recorded bat echolocation calls to measure overall activity, videotaped bat behavior and identified aquatic insects to determine whether bats were feeding or drinking, mist netted to assess visitation patterns with respect to season, sex, and reproductive condition for each of 4 species captured, studied movements of banded individuals, and monitored roosts of the California leaf-nosed bat (Macrotus californicus) in nearby mines. Echolocation activity was much higher at water than in nearby dry desert washes and was greater in dry washes than at random sites away from water. Bats visited water in all seasons, visiting primarily to drink, not to feed on insects. The California leaf-nosed bat constituted 41% of more than 1,000 captures. I concluded that in my study area this species made extensive use of water developments for drinking, particularly during lactation.

On the Colorado Plateau, environments occupied by Mexican spotted owls (Strix occidentalis lucida) receive intense levels of recreational activity that could adversely effect their behavior and reproductive success. Any spatial restrictions on recreational activities in these narrow canyons would likely eliminate all recreational activity within a given canyon. We assessed changes to activity budgets and nest attendance caused by hikers (Chapter 1) and examined factors that influenced flush responses of roosting owls to hikers (Chapter 2). We conclude that high levels of recreational activity in nesting habitat may be detrimental to Mexican spotted owls and recommend a 205-m radius buffer zone around occupied nests. Based on responses of roosting owls to hikers, we established response thresholds as a basis for exploring management options that will maximize protection of owls and minimize restrictions to recreationists.

The effects of fire on vegetation in the upper encinal woodlands, Santa Catalina Mountains, southeastern Arizona, were studied following a wildfire in July 1995. Similar unburned and burned sites were compared to determine differences (alpha = .05) for frequency, density, and percent cover of herbs, shrubs, and trees through observations made during early June of 1997 and 1998 (two and three years postfire). For herbs, which showed their opportunistic characters, differences existed for frequency and percent cover each year and density in the third year. For shrubs, due to the ability of the dominant species, Arctostaphylos pungens (pointleaf manzanita), to rapidly reseed itself, no differences existed for frequency or density each year; but total mortality of mature A. pungens resulted in differences for percent cover each year. For trees, due to the ability of Quercus spp. to vigorously stump sprout, no differences existed for frequency, density, or percent cover each year.

A study was done on a rocky intertidal community in Puerto Penasco, Sonora, Mexico in the summers of 1997--1999 in order to determine if the ENSO of 1997--1998 had an effect on population densities of selected macroinvertebrates. Two replicate transects were laid perpendicular to the sea edge and a census of 21 macroinvertebrate species was taken in the summers of 1997, 1998 and 1999. A significant decrease of species densities occurred in 1998 when the mean sea surface temperature (SST) was more than 2°C warmer than in 1997 due to the 1997--1998 ENSO event. A phenomenon was also observed in 1998 where some species changed, compared to 1997, their vertical distribution in the intertidal from shallow to deeper waters, with a subsequent return to a more expected distribution in 1999. Also a comparison of 1997 and 1976 densities showed an increase in 1997 in abundances of those species with southern geographic ranges and a decrease of those with northern geographic ranges. This was correlated with an increase of mean SST of 1.9°C between the 1970's and the 1990's.

Tree-ring records were used to reconstruct the spatial and temporal patterns of western spruce budworm (Choristoneura occidentalis Freeman) outbreaks in the Rio Grande National Forest (RGNF) of southern Colorado. Reconstructions at 11 host stands showed a synchronous pattern of outbreaks with a peak in the number of trees recording outbreaks over the entire RGNF on average every 24 years. These synchronous periods of outbreaks coincided with periods of increased moisture as indicated by an independently reconstructed summer Palmer Drought Severity Index, while relatively few trees recorded outbreaks during dry periods. The reconstruction on the RGNF does not support the hypothesis that human land use has significantly altered outbreak patterns. Tree response to outbreaks in the RGNF was different from prior studies as reductions in growth were typically detectable only when growth was compared to that of nonhost tree species.

No description available.

<p> Communication facilitates almost every social interaction between organisms and this communication is especially important for mate acquisition. Anuran amphibians are an excellent model system to study mate choice behaviors and sexual selection. In this work I recorded male calls of the spring peeper, <i> Pseudacris crucifer</i>, between two populations (Maryland and Louisiana) and analyzed call parameters such as frequency, duration, and rise and fall time. I found differences in the frequency and the frequency sweep of the calls. I conducted choice experiments to test female mating preferences in the Louisiana population and found a preference for longer calls over short calls. Females did not express a preference for frequency, frequency sweep, or local (LA) versus foreign (MD) calls. I also conducted multimodal signaling experiments on the t&uacute;ngara frog, <i>Physalaemus pustulosus</i>. I used natural calls and a robotic t&uacute;ngara frog to determine how females assess different signal modalities (auditory versus visual). I tested previously established attractive calls against unattractive calls, paired with the robo-frog and inflating vocal sac, to see if the visual stimulus would modulate the attractiveness of the call. The presence of the vocal sac did not make the unattractive call more attractive. The vocal sac may have important implications for localization in a more complex environment but here, it did not act as a mate attracting signal. This study provides the ground work necessary for multimodal signaling in spring peepers and for complex sensory environment choice tests in the t&uacute;ngara frog.</p>

Since its introduction to the U.S., the South American fire ant Solenopsis invicta has displaced its native congener S. geminata from many habitats. Repeated censusing indicates that the distribution of these ants in the northern Apalachicola National Forest is stable, with S. invicta monopolizing pond margins, both species occupying roadsides, and S. geminata found alone in the woods. A series of investigations revealed a number of differences between S. invicta and S. geminata that may play a role in determining the distribution of the two species. Attributes of S. invicta which have likely contributed to its displacement of S. geminata include: larger colony size, quicker colony growth facilitated by brood raiding, reproduction earlier in the year, and freedom from mermithid nematode parasitism. In the woods of the Apalachicola National Forest, the advantages enjoyed by S. invicta appear to be counteracted by a greater ability of S. geminata newly mated queens to survive the colony founding period. / Comparisons of the reproductive biology of S. invicta and S. geminata indicate striking differences. All mature S. invicta colonies are reproductively active during late spring and early summer, when mating flight activity is at its peak. Subsequently, the number of active colonies and the number of ants participating in mating flights gradually declines. The reproductive system of S. geminata is more complex, with colonies pursuing three different strategies. Two-thirds of the S. geminata colonies are reproductively active only in the late spring and early summer. About one-fifth are active only in the fall. A small number of colonies release alates in the spring/summer and again in the fall. The gynes of S. geminata exhibit a distinct dimorphism: those produced in spring and summer are larger, heavier, and fatter than gynes produced in fall. Both types are successful at becoming the sole queens of mature colonies, although several lines of evidence indicate that microgynes from fall mating flights do not found colonies independently. / Source: Dissertation Abstracts International, Volume: 55-04, Section: B, page: 1269. / Major Professor: Walter R. Tschinkel. / Thesis (Ph.D.)--The Florida State University, 1994.

The ecology and behavior of nine species of anemonefishes and ten species of sea anemones were studied at a variety of sites in the region of Madang, Papua New Guinea. More than 95% of the suitable anemones in the region were occupied by anemonefishes. Each species of fish had a distinct pattern of host specificity and population surveys at three replicate reef sites within four locations situated at varying distances from the mainland (nearshore, mid-lagoon, outer barrier, and offshore), indicated that each species of host anemone and anemonefish lived within a particular range of locations. Recruitment was monitored to anemones in natural populations and to anemones that had their resident fishes removed. Significantly more fish recruited to anemones without residents. Each fish species recruited into the host species and locations occupied by their adults. Thus, recruitment had a strong effect on patterns of anemonefish host specificity and distribution, but fish abundance was limited by the availability of anemones. / The host location and association behaviors of laboratory raised anemonefishes were examined. Juvenile anemonefishes that were competent to settle were released in the field at different distances and orientations away from anemones. The fishes were only attracted toward particular species of anemones, and they used chemical cues released from anemones and rheotaxis to locate their hosts. Resident fishes were aggressive toward new recruits and usually prevented them from staying with anemones. Recruiting anemonefishes contacted the tentacles of most anemone species without harm, but in some cases the fishes were stung. Forced contact tests with anemonefish eggs, larvae, juveniles, and adults showed that the fish species tested developed some level of protection from anemones during metamorphosis from a pelagic larva to a benthic juvenile. Forced contact tests with fishes reared in complete isolation from anemones demonstrated that the protection was innate for some species of anemonefishes. However, juvenile fishes still went through acclimation behavior during the initial interaction with an anemone, even if the fishes were innately protected. Immunological studies with polyclonal antibodies to anemone mucus antigens showed that anemonefishes acquire anemone antigens in their mucus coat during their association with anemones. / Source: Dissertation Abstracts International, Volume: 53-11, Section: B, page: 5524. / Major Professor: R. N. Mariscal. / Thesis (Ph.D.)--The Florida State University, 1992.