Search

Simple Summary: We examined a white-tailed deer (Odocoileus virginianus) population with evidence of decline in the Southern Appalachian region of the United States. In the Chattahoochee National Forest (CNF) in northern Georgia, deer harvest numbers and hunter success rates have drastically reduced over the last few decades, suggesting a decline in deer density. Low fawn survival (16%) was also recently recorded, prompting further concern regarding deer population sustainability. In the CNF, we radio-collared 14 yearling and 45 adult female white-tailed deer along with 71 fawns during 2018–2020 to estimate the annual survival and fecundity of each age class. We modeled future population growth (λ) over 10 years to evaluate the current rate of decline and various other management scenarios. Projections indicated that the white-tailed deer population will decline by an average of 4.0% annually under current conditions, and only scenarios that incorporated both antlerless harvest restrictions and improved fawn survival will lead to positive population growth. Thus, these approaches should be emphasized in future management plans within the Southern Appalachian region to facilitate recovery. This methodology can be applied by other wildlife managers with knowledge of site-specific vital rates to inform potential management strategies. Although generally abundant, white-tailed deer (Odocoileus virginianus) populations in the southeastern United States have recently experienced several localized declines attributed to reduced fawn recruitment following the establishment of coyotes (Canis latrans). The Southern Appalachians is a mountainous region suggested to be experiencing white-tailed deer declines, as harvest numbers and hunter success rates have substantially decreased in northern Georgia since 1979. Low fawn survival (16%) was also recently documented in the Chattahoochee National Forest (CNF) in northern Georgia, necessitating further examination. We radio-collared 14 yearling and 45 adult female white-tailed deer along with 71 fawns during 2018–2020 in the CNF to estimate field-based vital rates (i.e., survival and fecundity) and parameterize stage-structured population models. We projected population growth rates (λ) over 10 years to evaluate the current rate of decline and various other management scenarios. Our results indicated that the observed population would decline by an average of 4.0% annually (λ = 0.960) under current conditions. Only scenarios including antlerless harvest restrictions in addition to improved fawn survival resulted in positive growth (λ = 1.019, 1.085), suggesting these measures are likely necessary for population recovery in the region. This approach can be applied by wildlife managers to inform site-specific management strategies. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a new 400-ks Chandra X-ray observation of the merging galaxy cluster Abell 2146. This deep observation reveals detailed structure associated with the major merger event including the Mach number M= 2.3 ± 0.2 bow shock ahead of the dense, ram pressure stripped subcluster core and the first known example of an upstream shock in the intracluster medium (ICM) ( M= 1.6 ± 0.1). By measuring the electron temperature profile behind each shock front, we determine the time-scale for the electron population to thermally equilibrate with the shock-heated ions. We find that the temperature profile behind the bow shock is consistent with the time-scale for Coulomb collisional equilibration and the post-shock temperature is lower than expected for instant shock heating of the electrons. Although like the Bullet cluster the electron temperatures behind the upstream shock front are hotter than expected, favouring the instant heating model, the uncertainty on the temperature values is greater here and there is significant substructure complicating the interpretation. We also measured the width of each shock front and the contact discontinuity on the leading edge of the subcluster core to investigate the suppression of transport processes in the ICM. The upstream shock is ∼440 kpc in length but appears remarkably narrow over this distance with a best-fitting width of only 6+5−3 kpc compared with the mean free path of 23 ± 5 kpc. The leading edge of the subcluster core is also narrow with an upper limit on the width of only 2 kpc separating the cool, multiphase gas at 0.5-2 keV from the shock-heated surrounding ICM at ∼6 keV. The strong suppression of diffusion and conduction across this edge suggests a magnetic draping layer may have formed around the subcluster core. The deep Chandra observation has also revealed a cool, dense plume of material extending ∼170 kpc perpendicular to the merger axis, which is likely to be the disrupted remnant of the primary cluster core. This asymmetry in the cluster morphology indicates the merger has a non-zero impact parameter. We suggest that this also explains why the south-western edge of the subcluster core is narrow and stable over ∼150 kpc in length, but the north-eastern edge is broad and being stripped of material. [ABSTRACT FROM AUTHOR]

We present a new Chandra observation of the galaxy cluster Abell 2146 which has revealed a complex merging system with a gas structure that is remarkably similar to the Bullet cluster. The X-ray image and temperature map show a cool subcluster with a ram pressure stripped tail of gas just exiting the disrupted primary cluster. From the sharp jump in the temperature and density of the gas, we determine that the subcluster is preceded by a bow shock with a Mach number , corresponding to a velocity relative to the main cluster. We estimate that the subcluster passed through the primary core only ago. In addition, we observe a slower upstream shock propagating through the outer region of the primary cluster and calculate a Mach number . Based on the measured shock Mach numbers and the strength of the upstream shock, we argue that the mass ratio between the two merging clusters is between 3 and 4 to one. By comparing the Chandra observation with an archival Hubble Space Telescope observation, we find that a group of galaxies is located in front of the X-ray subcluster core but the brightest cluster galaxy is located immediately behind the X-ray peak. [ABSTRACT FROM AUTHOR]