Dispersal patterns of juvenile Townsend's ground squirrels in southwestern Idaho

1998 ◽  
Vol 76 (11) ◽  
pp. 2084-2089 ◽  
Author(s):  
Gail S Olson ◽  
Beatrice Van Horne
Keyword(s):  
Survival Rates ◽  
Habitat Type ◽  
Dispersal Distance ◽  
Ground Squirrels ◽  
Short Term ◽  
Dispersal Patterns ◽  
Conservation Area ◽  
Spermophilus Townsendii ◽  
Dispersal Distances ◽  
Two Parameter

Understanding the effects of habitat reduction or fragmentation on animals requires some knowledge of their dispersal patterns. We used radiotelemetry to examine dispersal characteristics of 59 (37 male and 22 female) juvenile Townsend's ground squirrels (Spermophilus townsendii) on the Snake River Birds of Prey National Conservation Area in southwestern Idaho from April to June in 1993 and 1994. We tested for differences between years, sexes, and habitats in the rates and distances of dispersal. We compared the fates of dispersers and nondispersers and tested whether the direction of dispersal differed from random and whether the distribution of dispersal distances could be fitted to a two-parameter exponential function. Of the 38 animals for which dispersal status could be determined, 16 dispersed. The proportion of dispersers was greater for males than for females, but these rates did not differ by year or habitat type. We found no differences between habitats in dispersal distance. Survival rates through immergence into estivation did not differ between dispersers and nondispersers, suggesting that dispersal is not risky over the short term. Direction of dispersal did not differ from random, and the distribution of dispersal distances was adequately fitted to a truncated exponential distribution with a truncation distance of 118 m. Dispersers tended to end up in the habitat type that they started in, suggesting the possibility of habitat imprinting.

scholarly journals Animal movement drives variation in seed dispersal distance in a plant–animal network

2019 ◽  
Vol 286 (1894) ◽  
pp. 20182007 ◽  
Author(s):  
E. Rehm ◽  
E. Fricke ◽  
J. Bender ◽  
J. Savidge ◽  
H. Rogers
Keyword(s):  
Seed Dispersal ◽  
Animal Movement ◽  
Bird Species ◽  
Dispersal Distance ◽  
Dispersal Patterns ◽  
Long Distance ◽  
Gut Passage ◽  
Dispersal Distances ◽  
Seed Dispersal Distance ◽  
Passage Times

Frugivores play differing roles in shaping dispersal patterns yet seed dispersal distance is rarely quantified across entire communities. We model seed dispersal distance using gut passage times and bird movement for the majority (39 interactions) of known bird–tree interactions on the island of Saipan to highlight differences in seed dispersal distances provided by the five avian frugivores. One bird species was found to be a seed predator rather than a disperser. The remaining four avian species dispersed seeds but differences in seed dispersal distance were largely driven by interspecific variation in bird movement rather than intraspecific variation in gut passage times. The median dispersal distance was at least 56 m for all species-specific combinations, indicating all species play a role in reducing high seed mortality under the parent tree. However, one species—the Micronesian Starling—performed 94% of dispersal events greater than 500 m, suggesting this species could be a key driver of long-distance dispersal services (e.g. linking populations, colonizing new areas). Assessing variation in dispersal patterns across this network highlights key sources of variation in seed dispersal distances and suggests which empirical approaches are sufficient for modelling how seed dispersal mutualisms affect populations and communities.

scholarly journals Informed dispersal of the dandelion

2019 ◽  
Author(s):  
Madeleine Seale ◽  
Oleksandr Zhdanov ◽  
Cathal Cummins ◽  
Erika Kroll ◽  
Mike Blatt ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Dispersal Distance ◽  
Functional Change ◽  
Short Term ◽  
Plant Dispersal ◽  
Informed Dispersal ◽  
Flight Capacity ◽  
The Common ◽  
Dispersal Distances ◽  
Common Dandelion

Animal migration is highly sensitised to environmental and biological cues, yet plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, is a classic example of a wind-dispersed plant and has an intricate haired pappus facilitating flight. This pappus facilitates enables the formation of a separated vortex ring (SVR) during flight (1); however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. Here we characterise the biomechanical function of the pappus morphing regarding SVR dynamics and flight capacity. When the pappus closes, the falling velocity is greatly increased and the velocity deficit within the vortex decreased. To understand the implications of this structural-functional change, we used historic meteorological data to simulate dispersal distance. Dispersal distances were reduced with the pappus closed, and so was detachment. We propose that moisture-dependent pappus-morphing serves to retain seeds in favourable moist niches, providing a form of informed dispersal (2) that has not been characterised in plants on such a short-term, responsive time scale (3).

scholarly journals Natal Dispersal of the Spotted Owl in Southern California: Dispersal Profile of an Insular Population

The Condor ◽  
2001 ◽  
Vol 103 (4) ◽  
pp. 691-700 ◽  
Author(s):  
William S. Lahaye ◽  
R. J. Gutiérrez ◽  
Jeffrey R. Dunk
Keyword(s):  
Southern California ◽  
Dispersal Distance ◽  
Dispersal Patterns ◽  
San Bernardino Mountains ◽  
Sibling Pairs ◽  
Strix Occidentalis ◽  
San Bernardino ◽  
The Difference ◽  
Dispersal Distances ◽  
Insular Population

Abstract We studied the dispersal patterns of an insular population of California Spotted Owls (Strix occidentalis occidentalis) in southern California from 1987–1998. The study area encompassed the entire San Bernardino Mountains and included a nested, 535-km2 study area which we used to evaluate the effects of study area size on dispersal parameter estimation. One hundred and twenty-nine of the 478 banded juvenile owls (27%) had entered the territorial population by 1998. Over half of the successful dispersers became territorial within one year. Additionally, all females and 95% of the males occupied territories within three years. Twenty-three sibling pairs and one set of triplets dispersed successfully. Sibling dispersal distances were not correlated. Sixty-seven males and 62 females dispersed 2.3–36.4 km (mean ± SD = 10.1 ± 7.6 km) and 0.4–35.7 km (mean ± SD = 11.7 ± 8.1 km), respectively. The difference between male and female mean dispersal distances was not significant. Dispersal distance and first-year survival were underestimated when using data collected within the smaller, nested study area. The presence of conspecifics may play a key role in the settling process. Seventy-eight percent of the dispersers settled in territories that were occupied by either pairs or single owls the previous year, 16% settled in vacant territories next to occupied sites, and 6% settled at sites of unknown occupancy. No owls settled at unoccupied sites that were not adjacent to occupied sites. Dispersión Natal de Strix occidentalis occidentalis: Descripción de la Dispersión de una Población Insular Resumen.  Estudiamos los patrones de dispersión de una población insular de lechuza moteada californiana (Strix occidentalis occidentalis) en el sur de California, desde 1987–1998. El área de estudio comprendió las montañas de San Bernardino e incluyó un sito de estudio de 535 km2 incluído en esta zona el cual usamos para evaluar el efecto del tamaño del área de estudio para la estimación de los parámetros de dispersión. Hasta 1998, 129 de las 478 lechuzas juveniles marcadas (27%) habían entrado a la población territorial. Más la mitad de los dispersores exitosos se hicieron territoriales al cabo de un año. Adicionalmente, todas las hembras y el 95% de los machos ocuparon territorios al cabo de tres años. Veintitrés pares de hermanos y un triplete se dispersaron exitosamente. La distancia de dispersión entre hermanos no se correlacionó. Sesenta y siete machos y 62 hembras se dispersaron 2.3–36.4 km (media = 10.1 ± 7.6 km) y 0.4–35.7 km (media = 11.7 ± 8.1 km), respectivamente. La diferencia entre la media de la distancia de dispersión entre hembras y machos no fue significativa. La distancia de dispersión y supervivencia del primer año fueron subestimadas cuando se utilizaron los datos colectados en la sub-área de estudio de menor tamaño. La presencia de conespecíficos puede representar un factor clave en el proceso de asentamiento. Setenta y ocho por ciento de los dispersores se asentaron en territorios que habían estado ocupados por parejas o lechuzas no emparejadas el año anterior, el 16% en territorios no ocupados próximos a sitios ocupados, y el 6% se asentó en sitios con ocupación desconocida. Ninguna lechuza se asentó en sitios desocupados que no estuvieran adyacentes a un sitio ocupado.

scholarly journals Robotic and laparoscopic liver surgery for colorectal liver metastases: an experience from a German Academic Center

2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Mirhasan Rahimli ◽  
Aristotelis Perrakis ◽  
Vera Schellerer ◽  
Andrew Gumbs ◽  
Eric Lorenz ◽  
...  
Keyword(s):  
Abdominal Surgery ◽  
Minimally Invasive ◽  
Liver Surgery ◽  
Colorectal Liver Metastases ◽  
Survival Rates ◽  
Long Term Outcomes ◽  
Short Term ◽  
Minimally Invasive Liver Surgery ◽  
Previous Abdominal Surgery

Abstract Background Minimally invasive liver surgery (MILS) in the treatment of colorectal liver metastases (CRLM) is increasing in incidence. The aim of this work was to present our experience by reporting short-term and long-term outcomes after MILS for CRLM with comparative analysis of laparoscopic (LLS) and robotic liver surgery (RLS). Methods Twenty-five patients with CRLM, who underwent MILS between May 2012 and March 2020, were selected from our retrospective registry of minimally invasive liver surgery (MD-MILS). Thirteen of these patients underwent LLS and 12 RLS. Short-term and long-term outcomes of both groups were analyzed. Results Operating time was significantly longer in the RLS vs. the LLS group (342.0 vs. 200.0 min; p = 0.004). There was no significant difference between the laparoscopic vs. the robotic group regarding length of postoperative stay (8.8 days), measured blood loss (430.4 ml), intraoperative blood transfusion, overall morbidity (20.0%), and liver surgery related morbidity (4%). The mean BMI was 27.3 (range from 19.2 to 44.8) kg/m2. The 30-day mortality was 0%. R0 resection was achieved in all patients (100.0%) in RLS vs. 10 patients (76.9%) in LLS. Major resections were carried out in 32.0% of the cases, and 84.0% of the patients showed intra-abdominal adhesions due to previous abdominal surgery. In 24.0% of cases, the tumor was bilobar, the maximum number of tumors removed was 9, and the largest tumor was 8.5 cm in diameter. The 1-, 3- and 5-year overall survival rates were 84, 56.9, and 48.7%, respectively. The 1- and 3-year overall recurrence-free survival rates were 49.6 and 36.2%, respectively, without significant differences between RLS vs. LLS. Conclusion Minimally invasive liver surgery for CRLM is safe and feasible. Minimally invasive resection of multiple lesions and large tumors is also possible. RLS may help to achieve higher rates of R0 resections. High BMI, previous abdominal surgery, and bilobar tumors are not a barrier for MILS. Laparoscopic and robotic liver resections for CRLM provide similar long-term results which are comparable to open techniques.

scholarly journals Subtle short-term physiological costs of an experimental augmentation of fleas in wild Columbian ground squirrels

2019 ◽  
Vol 222 (12) ◽  
pp. jeb203588
Author(s):  
Jeffrey D. Roth ◽  
F. Stephen Dobson ◽  
François Criscuolo ◽  
Pierre Uhlrich ◽  
Alexandre Zahariev ◽  
...  
Keyword(s):  
Ground Squirrels ◽  
Short Term ◽  
Columbian Ground Squirrels

Evolution of Surgical Approaches in the Treatment of Petroclival Meningiomas: A Retrospective Review

2007 ◽  
Vol 61 (suppl_5) ◽  
pp. ONS202-ONS211 ◽  
Author(s):  
Nicholas C. Bambakidis ◽  
U. Kumar Kakarla ◽  
Louis J. Kim ◽  
Peter Nakaji ◽  
Randall W. Porter ◽  
...  
Keyword(s):  
Survival Rates ◽  
Progression Free Survival ◽  
Surgical Approaches ◽  
Single Institution ◽  
Short Term ◽  
Total Resection ◽  
Free Survival ◽  
Petroclival Meningioma ◽  
Petroclival Meningiomas

Abstract Objective: We examined the surgical approaches used at a single institution to treat petroclival meningioma and evaluated changes in method utilization over time. Methods: Craniotomies performed to treat petroclival meningioma between September of 1994 and July of 2005 were examined retrospectively. We reviewed 46 patients (mean follow-up, 3.6 yr). Techniques included combined petrosal or transcochlear approaches (15% of patients), retrosigmoid craniotomies with or without some degree of petrosectomy (59% of patients), orbitozygomatic craniotomies (7% of patients), and combined orbitozygomatic-retrosigmoid approaches (19% of patients). In 18 patients, the tumor extended supratentorially. Overall, the rate of gross total resection was 43%. Seven patients demonstrated progression over a mean of 5.9 years. No patients died. At 36 months, the progression-free survival rate for patients treated without petrosal approaches was 96%. Of 14 patients treated with stereotactic radiosurgery, none developed progression. Conclusion: Over the study period, a diminishing proportion of patients with petroclival meningioma were treated using petrosal approaches. Utilization of the orbitozygomatic and retrosigmoid approaches alone or in combination provided a viable alternative to petrosal approaches for treatment of petroclival meningioma. Regardless of approach, progression-free survival rates were excellent over short-term follow-up period.

scholarly journals Interacting effects of forest fragmentation and howler monkey foraging on germination and disperal of fig seeds

Oryx ◽  
2002 ◽  
Vol 36 (3) ◽  
pp. 266-271 ◽  
Author(s):  
Juan Carlos Serio-Silva ◽  
Victor Rico-Gray
Keyword(s):  
Dispersal Distance ◽  
Alouatta Palliata ◽  
Howler Monkey ◽  
Forest Fragment ◽  
Howler Monkeys ◽  
Conservation Policies ◽  
Dispersal Distances ◽  
Alouatta Palliata Mexicana ◽  
Fragmented Forests ◽  
Individual Trees

We studied changes in germination rates and dispersal distance of seeds of Ficus perforata and F. lundelli dispersed by howler monkeys (Alouatta palliata mexicana), in a small (40 ha) ‘disturbed’ and a larger (>600 ha) ‘preserved’ tropical rainforest in southern Veracruz, Mexico. The interaction between A. p. mexicana and Ficus (Urostigma) spp. is beneficial for the interacting species and has important implications for their conservation. Howler monkeys gain from the ingestion of an important food source, germination rates of Ficus seeds are improved by passage through the monkeys' digestive tract, and the seeds are more likely to be deposited in a site suitable for germination and development. Seed dispersal distances are relatively larger in the preserved site, with both the size of the forest area and the spatial pattern of Ficus affecting the dispersal process. In a large forest fragment with ‘regularly’ distributed Ficus individuals the howler monkeys move away from the seed source, increasing the probability that the seeds are desposited on a tree other than Ficus, which is important for the germination and future development of a hemiepiphytic species. In a small forest fragment with trees distributed in clumps howlers repeatedly use the same individual trees, and faeces containing seeds may be dropped on unsuitable trees more often. These are key issues when addressing conservation policies for fragmented forests.

scholarly journals Dispersal Kernel Determines Symmetry of Spread and Geographical Range for an Insect

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Jeffrey D. Holland
Keyword(s):  
Sugar Maple ◽  
Spatial Dynamics ◽  
Geographic Range ◽  
Dispersal Distance ◽  
Dispersal Kernel ◽  
Geographical Range ◽  
Spatial Distributions ◽  
Longhorned Beetle ◽  
Ecological Patterns ◽  
Dispersal Distances

The distance from a source patch that dispersing insects reach depends on the number of dispersers, or random draws from a probability density function called a dispersal kernel, and the shape of that kernel. This can cause asymmetrical dispersal between habitat patches that produce different numbers of dispersers. Spatial distributions based on these dynamics can explain several ecological patterns including megapopulations and geographic range boundaries. I hypothesized that a locally extirpated longhorned beetle, the sugar maple borer, has a new geographical range shaped primarily by probabilistic dispersal distances. I used data on occurrence from Ontario, Canada to construct a model of geographical range in Indiana, USA based on maximum dispersal distance scaled by habitat area. This model predicted the new range boundary within 500 m very accurately. This beetle may be an ideal organism for exploring spatial dynamics driven by dispersal.

Concrete Fatigue Life Characteristics of the Different Survival Rates in the Lateral Pressure Conditions

2012 ◽  
Vol 600 ◽  
pp. 250-255
Author(s):  
Qiang Cai ◽  
Ji Ming Kong ◽  
Ze Fu Chen
Keyword(s):  
Fatigue Life ◽  
Life Stress ◽  
Failure Modes ◽  
Survival Curve ◽  
Survival Rates ◽  
Life Distribution ◽  
Fatigue Design ◽  
Set Up ◽  
Fatigue Equation ◽  
Two Parameter

Under cyclic loading of concrete structures, fatigue failure is the main failure modes of fatigue, which has become the fatigue design of concrete structure must be considered, then the concrete fatigue studies must clarify the fatigue life of concrete under different survival curve S-N curve. Based on the statistics of the two parameter Weibull distribution theory, obtain the concrete under different survival rates of fatigue life distribution, namely to improve survival, reduce the fatigue life; stress level is reduced, the fatigue life is increased; and has set up more than 50% under different survival rates of concrete fatigue equation.

Responses of lizards to three experiments fires in the savanna forests of Kakadu National Park

1994 ◽  
Vol 21 (2) ◽  
pp. 131 ◽  
Author(s):  
CR Trainor ◽  
JCZ Woinarski
Keyword(s):  
National Park ◽  
Habitat Type ◽  
Detrended Correspondence Analysis ◽  
Fire Regimes ◽  
Direct Effects ◽  
Short Term ◽  
Lizard Species ◽  
Savanna Communities ◽  
Induced Changes ◽  
Term Response

A species-rich lizard community responded variably to a range of experimental fire regimes in a tropical savanna. Heteronotia binoei was the only lizard species that showed a short-term response to fire, decreasing in abundance directly after the early- and late-burns. H. binoei and Diporiphora bilineata were significantly more abundant in early-burn treatments. Carlia amax was more abundant in unburnt and early-burn treatments. C. munda was more abundant in unburnt and early-burn sites. Differences in the relative abundance of species between treatments is attributed to site differences in vegetation structure, and fire-induced changes to the structure of habitat. Early-burn sites were significantly richer in lizard species (P< 0.05); however, overall lizard abundance, Shannon-Wiener diversity and Detrended Correspondence Analysis (DCA) 1 and DCA 2 scores were not significantly different, suggesting that habitat partitioning has a stronger influence than the direct effects of fire. Many lizards were associated with a direct gradient of moisture availability, including a seepage assemblage, with Carlia gracilis and Sphenomorphus darwiniensis correlated with increased moisture, a well-developed canopy and abundant leaf litter. An assemblage associated with the drier end of the gradient included Carlia triacantha, Ctenotus kurnbudj, Diporiphora magna and D. bilineata. The lizard composition of most quadrats was intermediate along the moisture gradient and was associated with typical eucalypt savanna communities. Lizard species that largely are restricted to the moist seepage zones may be particularly sensitive to late dry-season fires which alter this habitat type.

Sign in / Sign up

Export Citation Format

Share Document