Annual Population Growth Rate Research Articles

Endangered Green Turtles (Chelonia mydas) of the Northern Mariana Islands: Nesting Ecology, Poaching, and Climate Concerns

Marine turtles in the western Pacific remain threatened by anthropogenic impacts, but the region lacks long-term biological data for assessing conservation status and trends. The Central West Pacific (CWP) population of green turtles (Chelonia mydas) was listed as Endangered by the U.S. in 2016, highlighting a need to fill existing data gaps. This study focuses on the subset of this population nesting in the Commonwealth of the Northern Mariana Islands (CNMI). Using 11 years of nesting data, we (i) estimate reproductive demographic parameters, (ii) quantify abundance and trends, and (iii) estimate the impacts of anthropogenic threats, such as poaching of nesting females and increasing sand temperatures. In 2006-2016, nesting beach surveys, identification tagging, and nest excavations were conducted on Saipan, and rapid assessments of nesting activity were conducted on Tinian and Rota. On Saipan, temperature data-loggers were deployed inside nests and evidence of poaching (adults and eggs) was recorded. This study documents year-round nesting with a peak in March–July. Nester abundance for the three islands combined was 12 ± 6 (mean ± standard deviation) females annually, with at least 63 ± 35 nests observed per year. For 39 tagged individuals, straight carapace length was 95.6 ± 4.5 cm, remigration interval was 4.6 ± 1.3 years, and somatic growth was 0.3 ± 0.2 cm yr-1. Reproductive parameter estimates included clutch frequency of 7 ± 1.3 nests per female, inter-nesting interval of 11.4 ± 0.9 days, clutch size of 93 ± 21 eggs, incubation period of 55 ± 6.4 days, hatching success of 77.9% ± 27.0, and emergence success of 69.6% ± 30.3. Mean nest temperature of 30.9 ± 1.5°C was above the pivotal threshold of 29.0°C for temperature dependent sex determination, suggesting a female-bias may already exist. Model results suggest (i) hatching success decreases and embryonic death increases when nests experience maximum temperatures beyond 34°C, and (ii) embryonic death increases in nests with mean temperatures beyond 31°C. On Saipan, 32% of nesters were poached, reducing the annual population growth rate from 11.4% to 7.4%. This study provides the first comprehensive assessment of a nesting green turtle population in the Mariana Archipelago.

Urban Land Grabbing Mayhem in Douala Metropolitan Local Council Areas, Cameroon

Anarchical land conquest in developing world cities is virally infecting Cameroonian cities epitome by its largest metropolis. This is what this paper sought to portray of the successive augmentation of the Douala V Local Council urban space distinct by a weird anarchy-driven population growth. It posits that it is not just available unoccupied space but institutional indolence has of recent hemmed in urban infrastructural disorder that has led slums grow beyond bounds. Multi-temporal Landsat images for 1975 and 2015 and a Spot image of 1995 were used to determine the spatial colonization and expansion land use/land cover analyses. Results were corroborated with field information through field surveys using structured questionnaires. Findings permitted us note that space colonisation in Douala V experienced a 60.18% upward trend of built-up areas just in four decades (1975-2015), with a 1.5% annual population growth rate. Implications on the urbanscape have been an accelerated and severely degraded forest and natural vegetation form the 1403% growth urban human surge in 42 years (from 57,000 1975 to 800,000 inhabitants in 2017). Douala V thus emerged as an “try and see” land colonisation territory where new arrival of inhabitants inadvertently sowed structural anarchy valued at 51% permanent and 49% temporary structures. Noting that such disorder emanates from top-down urban governance and management this study recommends that urban planning legislation concerning must be inclusive of grass roots to guarantee involment as a canon of sustainable development in modern and post-modern times.

Individual‐Based Modeling of Delta Smelt Population Dynamics in the Upper San Francisco Estuary III. Effects of Entrainment Mortality and Changes in Prey

AbstractWe used an individual‐based model, developed previously for the endangered, endemic Delta Smelt Hypomesus transpacificus, to investigate two factors widely believed to affect its abundance in the San Francisco Estuary: entrainment in large water diversion facilities and declines and species shifts in their zooplankton prey. Previous analyses suggested that these factors had substantial effects on the Delta Smelt population, although evidence is accumulating that other factors, such as contaminants and predation, are also having effects. Simulations were performed for 1995–2005 with either entrainment mortality set to zero or zooplankton biomasses replaced with values sampled from pre‐decline years. The detailed individual‐based and spatial model output was summarized as the annual finite population growth rate (λ). Eliminating entrainment mortality increased the geometric mean λ by 39% through increased survival of larvae and adults. Substituting historical food for present‐day food resulted in variable annual λ values with a geometric mean that was 41% greater than the baseline value (14–81% across 10 alternative food scenarios). Historical food caused higher juvenile consumption and growth rates, leading to larger recruits, earlier maturity, and higher individual fecundity. These results were robust to four sets of simulations using alternative formulations for density dependence, mortality, maturity, and larval growth.

Changes in nesting success and breeding abundance of Spectacled Eiders Somateria fischeri in the Chaun Delta, Chukotka, Russia, 2003–2016

The Spectacled Eider Somateria fischeri is a rare sea duck confined to breeding in the Yukon–Kuskokwim Delta and Arctic coasts of Alaska and Russia. Almost nothing is known about its status and breeding biology in the Russian Arctic. Stratified systematic nest searches were conducted annually of Spectacled Eider nests on Ayopechan Island in the Chaun Delta, Arctic Russia during 2003–2016. Mean nest densities were stable during 2003–2009 but declined by 8.0% per annum during 2009–2016. Mean clutch size and annual female survival did not change over the same period, during which time annual nest survival and hatching success declined significantly. A simple three age-class matrix model estimated annual asymptotic population growth rate (λ) using observed fecundity from the beginning (1.1 hatched chick per female, λ = 0.864) and end (0.45 hatched chick per female, λ = 0.828) of the study period. This confirmed that to stabilize this population required three immigrant recruits for every local recruit at the beginning of the study and nine towards the end. Declines in annual nest survival appear correlated with (i) declines in nesting Sabine’s Gulls Xema sabini and Arctic Terns Sterna paradisaea with which nesting Spectacled Eiders associated and may have gained protection from predators, and (ii) marginally significant increases in large gull and mammalian predators at the site. Should current trends in nest density and fecundity continue, the survival of this breeding Spectacled Eider population is in jeopardy.

Sooty FalconFalco concolorreproduction and population dynamics on the islands in the Sea of Oman

Knowledge of demographic parameters affecting population dynamics is critical to the formulation of effective conservation strategies. Sooty FalconFalco concoloris a little‐studied, Near‐threatened species; estimates of global population size and trend for this species are uncertain. They lay eggs during mid‐summer and sometimes nest in colonies. This unusual breeding ecology suggests that demographic parameters driving their population growth rate may differ from those of most other falcons. We studied Sooty Falcon reproduction at breeding aggregations on Fahal Island and the Daymaniyat islands in the Sea of Oman during 2007–2014, modelled population growth and identified important life history parameters using elasticity analysis. The mean (± se) clutch and brood size was 2.83 ± 0.06 and 2.11 ± 0.07, respectively. Overall, 11.7% of nests failed between the egg and nestling stages, and the failure rate differed significantly between Fahal and the Daymaniyats, and across years. The mean proportion of eggs that hatched annually was 0.66 ± 0.02, and broods were significantly smaller on the Daymaniyats than on Fahal. Falcons on Fahal Island had a higher rate of hatching, a higher rate of nests that produced at least one chick, and produced more chicks per nest than on the Daymaniyats. We suggest that Fahal's proximity to the mainland gives breeding Sooty Falcons access to a more plentiful and stable source of food, especially during the period between arrival from the wintering grounds and the onset of the autumn migration of prey birds, resulting in the better reproductive rates for falcons on Fahal Island, relative to those on the Daymaniyat Islands. The annual asymptotic population growth rate (λ) was 0.87 (95% confidence interval (CI) 0.75–0.99), suggesting a declining population, although Sooty Falcons enjoyed a slightly higher population growth rate on Fahal than on the Daymaniyats. Because our study population is on the edge of the breeding range and is isolated from other breeding areas, measures to improve reproductive success of Sooty Falcons breeding on the islands in the Sea of Oman could be important for conservation of Sooty Falcons in Oman.

Impacts of Higher Education Institutions on Local Population and Employment Growth

We examine the relationship between higher education institutions (HEIs) and local population and employment growth, using a sample of fifty-seven New Zealand territorial local authorities between 1986 and 2013. We account for HEI endogeneity by estimating with difference generalized method of moments; by including lagged growth plus a large set of other controls; and by including official demographic projections to account for growth-related factors, including university student numbers, which were projected by official statisticians but are otherwise unobservable to the econometrician. Holding all else equal, we find that a greater share of university equivalent full-time students (EFTS) to working-age population raises population and employment growth. At the means, a one percentage point increase in the university EFTS share is associated with a 0.19 (0.14) percentage point increase in the annual average population (employment) growth rate. This (significant) relationship holds under virtually all alternative specifications, including different HEI activity definitions, samples, and specifications. Growth related to polytechnic activity is much weaker and is estimated far less precisely. Consistent with urbanization (but not localization) externalities, we find no evidence for complementarities between HEI activity and several innovation-related area characteristics, possibly reflecting the primary industry base of New Zealand.

Fatalities at wind turbines may threaten population viability of a migratory bat

Large numbers of migratory bats are killed every year at wind energy facilities. However, population-level impacts are unknown as we lack basic demographic information about these species. We investigated whether fatalities at wind turbines could impact population viability of migratory bats, focusing on the hoary bat (Lasiurus cinereus), the species most frequently killed by turbines in North America. Using expert elicitation and population projection models, we show that mortality from wind turbines may drastically reduce population size and increase the risk of extinction. For example, the hoary bat population could decline by as much as 90% in the next 50years if the initial population size is near 2.5 million bats and annual population growth rate is similar to rates estimated for other bat species (λ=1.01). Our results suggest that wind energy development may pose a substantial threat to migratory bats in North America. If viable populations are to be sustained, conservation measures to reduce mortality from turbine collisions likely need to be initiated soon. Our findings inform policy decisions regarding preventing or mitigating impacts of energy infrastructure development on wildlife.

ESTIMATION OF CO2 EMISSIONS OF THE VEHICLES TRANSPORT SECTOR IN THE STATE OF KUWAIT

During the past decades, the State of Kuwait has witnessed population growth, significant economic development and a rise in the level of income. This has resulted in a significant increase in the number of vehicles, which is vital for the local inhabitants and this has led to increased air pollutants, particularly in urban areas. This study aims to estimate the emission of carbon dioxide from the transport sector in The State of Kuwait using IPCC guidelines for national greenhouse gas inventories for the period from 2001 to 2010. According to the policy analysis made, there are no policies directly aimed at reducing the number of registered vehicles which shown an increase of 6% per year for the same period as compared to an annual population growth rate of 2.67%. Finally, contribution of vehicular emissions of CO 2 , especially in urban areas, was estimated by the results of this study, and thus it is recommended that policies be developed to especially reduce the growing number of vehicles. Additional recommendations include the acceleration of the implementation of high efficiency mass transport projects. Furthermore, the use of awareness campaigns for citizens is highly recommended.

Immigration ensures population survival in the Siberian flying squirrel.

Linking dispersal to population growth remains a challenging task and is a major knowledge gap, for example, for conservation management. We studied relative roles of different demographic rates behind population growth in Siberian flying squirrels in two nest‐box breeding populations in western Finland. Adults and offspring were captured and individually identifiable. We constructed an integrated population model, which estimated all relevant annual demographic rates (birth, local [apparent] survival, and immigration) as well as population growth rates. One population (studied 2002–2014) fluctuated around a steady‐state equilibrium, whereas the other (studied 1995–2014) showed a numerical decline. Immigration was the demographic rate which showed clear correlations to annual population growth rates in both populations. Population growth rate was density dependent in both populations. None of the demographic rates nor the population growth rate correlated across the two study populations, despite their proximity suggesting that factors regulating the dynamics are determined locally. We conclude that flying squirrels may persist in a network of uncoupled subpopulations, where movement between subpopulations is of critical importance. Our study supports the view that dispersal has the key role in population survival of a small forest rodent.

Preliminary study on alterations of altitude road traffic in China from 2006 to 2013.

IntroductionRoad traffic can play an important role in strengthening regional economic activities, especially at high altitude, and it is necessary to know important traffic-related information. Although previous studies reported on road traffic in China, there has been little research on high-altitude road traffic to date.MethodThe annual official census of road traffic safety from 2006 to 2013 was used to obtain data on the general population, registered drivers, registered vehicles, newly built roads, road traffic accidents (RTAs), mortality rate per 100 000 populations and per 10 000 vehicles in high-altitude provinces, including Tibet, Qinghai, Xinjiang, Gansu, Yunnan, Sichuan, and Chongqing. These provincial data were reviewed retrospectively, with the national data as the reference. Statistical analysis (i.e., t test) was used to compare the estimated average annual change rate of population, number of registered drivers, registered vehicles, and newly built roads in high-altitude provinces with the national rates.ResultsCompared with the national data, there are significantly higher annual rates of population growth in Tibet and Xinjiang, registered drivers in Gansu, registered vehicles in Gansu, Sichuan, and Chongqing, and newly built roads in Tibet and Qinghai. Among the investigated provinces, Tibet, Qinghai, and Yunnan had a higher proportion of the roads with the high class. RTAs and RTA-induced casualties in the high-altitude provinces indicated a decreasing trend. The mortality rate per 10 000 vehicles and per 100 000 populations showed a decreasing trend, while the RTA-related mortality rate in Tibet, Qinghai, Xinjiang and Gansu remained high.ConclusionsMajor changes for road traffic in high-altitude provinces have occurred over the past decade; however, the RTA-related mortality rate in high-altitude provinces has remained high. This study furthers understanding about road traffic safety in China; further studies on road traffic safety at high altitude should be performed.

Monitoring Agricultural Expansion in Burkina Faso over 14 Years with 30 m Resolution Time Series: The Role of Population Growth and Implications for the Environment

Burkina Faso ranges amongst the fastest growing countries in the world with an annual population growth rate of more than three percent. This trend has consequences for food security since agricultural productivity is still on a comparatively low level in Burkina Faso. In order to compensate for the low productivity, the agricultural areas are expanding quickly. The mapping and monitoring of this expansion is difficult, even on the basis of remote sensing imagery, since the extensive farming practices and frequent cloud coverage in the area make the delineation of cultivated land from other land cover and land use types a challenging task. However, as the rapidly increasing population could have considerable effects on the natural resources and on the regional development of the country, methods for improved mapping of LULCC (land use and land cover change) are needed. For this study, we applied the newly developed ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model) framework to generate high temporal (8-day) and high spatial (30 m) resolution NDVI time series for all of Burkina Faso for the years 2001, 2007, and 2014. For this purpose, more than 500 Landsat scenes and 3000 MODIS scenes were processed with this automated framework. The generated ESTARFM NDVI time series enabled extraction of per-pixel phenological features that all together served as input for the delineation of agricultural areas via random forest classification at 30 m spatial resolution for entire Burkina Faso and the three years. For training and validation, a randomly sampled reference dataset was generated from Google Earth images and based on expert knowledge. The overall accuracies of 92% (2001), 91% (2007), and 91% (2014) indicate the well-functioning of the applied methodology. The results show an expansion of agricultural area of 91% between 2001 and 2014 to a total of 116,900 km². While rainfed agricultural areas account for the major part of this trend, irrigated areas and plantations also increased considerably, primarily promoted by specific development projects. This expansion goes in line with the rapid population growth in most provinces of Burkina Faso where land was still available for an expansion of agricultural area. The analysis of agricultural encroachment into protected areas and their surroundings highlights the increased human pressure on these areas and the challenges of environmental protection for the future.

Bison Conservation in Northern Great Plains National Parks: No Need to Panic

Bison (Bison bison) are a keystone species in the North American Great Plains. They are also a species of conservation concern in part because they suffered a severe population bottleneck at the end of the 19th century and now exist in mostly small and isolated populations. Wind Cave National Park introduced 20 bison in 1913–16; Theodore Roosevelt National Park introduced 29 animals to a South Unit in 1956 and subsequently transferred 20 bison from that herd to the park's North Unit in 1962; and Badlands National Park introduced 53 animals in 1963–64 and another 20 in 1984. The four herds are confined within fences, and no known introduction of new bison into the gene pools has occurred. The four herds are routinely culled down to approximately 425, 350, 200, and 700 animals, respectively. I found no evidence of inbreeding depression as measured by annual population growth and reproductive rates. A population viability analysis also failed to find persuasive evidence of inbreeding depression. Under current management scenarios, gene diversity in 100 years should remain above levels currently known to cause inbreeding depression in bison. I found no compelling reason to introduce new bison into the herds or transfer bison between herds in the foreseeable future.

Spatial modelling of land use/cover change (LUCC) in South Tangerang City, Banten

Urban expansion in peri-urban region remains a major issue for regional planning and development, as it converts most of the land cover into built-up settlements rapidly and extensively beyond its spatial allocation plan (RTRW). South Tangerang City is one of municipalities in Jabodetabek with the most rapid annual population growth rate reached 6.87%. LUCC analysis from three LANDSAT land cover maps (1990, 2002, and 2014) shows that the built-up area has increased 8 times (8650 ha) in 1990-2014 with the average annual growth rate of 10.83% per sub-district (kelurahan). The most extensive land conversion type in 1990-2002 was vegetated land to open land (3605ha), while in 2002-2014 land conversion type was dominated by open land to built-up (3446ha). In general, the built-up area expansion in 1990-2002 shows irregular ribbon development pattern in district Serpong Utara, Pondok Aren, Ciputat Timur, Ciputat, and Pamulang, while district Serpong tends to represent leap frog development pattern. The expansion in 2002-2014 shows infill and ribbon development pattern continuation across the city. MLP was used to model LUCC sensitivity prediction. The model performance shows 73.16% accuracy with ROC validation of prediction output reaches 0.804 for 2014, which is qualified to predict LUCC sensitivity in 2032.

Different population responses of three sympatric rodent species to acorn masting—the role of tannin tolerance

AbstractRodent population dynamics are predicted to respond positively to the masting of acorns, but diverging results have been published. This study tested the hypothesis that population responses to acorn masting vary depending on differences in the tolerance to tannins of different rodent species. The effects of acorn abundance on the rodent population densities were analyzed using a dataset obtained in Hokkaido, Japan. Specifically, population fluctuations of three rodent species (Apodemus speciosus, A. argenteus, and Myodes rufocanus) and the abundance of Quercus crispula acorns have been monitored since 1992. Acorn production in previous years had a positive effect on the annual population growth rates of A. speciosus; however, this trend was not clear in the other two species. Tannin tolerance, assessed by body weight changes in an acorn feeding experiment, exhibited clear differences among the rodent species; namely, the body weight of A. speciosus increased, whereas that of the other two species decreased. The observed responses to acorn masting of populations of the three sympatric rodent species reflected tannin tolerance. It suggests that only populations of species with high tannin tolerance positively respond to acorn masting. Previous studies tend to overlook species‐specific abilities of coping with tannins in acorns. Our results emphasize the necessity of evaluating the tannin tolerance of rodents and the tannin content of acorns to understand how rodent population dynamics and acorn production are related.

Seasonal survival estimation for a long-distance migratory bird and the influence of winter precipitation.

Conservation of migratory animals requires information about seasonal survival rates. Identifying factors that limit populations, and the portions of the annual cycle in which they occur, are critical for recognizing and reducing potential threats. However, such data are lacking for virtually all migratory taxa. We investigated patterns and environmental correlates of annual, oversummer, overwinter, and migratory survival for adult male Kirtland's warblers (Setophaga kirtlandii), an endangered, long-distance migratory songbird. We used Cormack-Jolly-Seber models to analyze two mark-recapture datasets: 2006-2011 on Michigan breeding grounds, and 2003-2010 on Bahamian wintering grounds. The mean annual survival probability was 0.58±0.12 SE. Monthly survival probabilities during the summer and winter stationary periods were relatively high (0.963±0.005 SE and 0.977±0.002 SE, respectively). Monthly survival probability during migratory periods was substantially lower (0.879±0.05 SE), accounting for ~44% of all annual mortality. March rainfall in the Bahamas was the best-supported predictor of annual survival probability and was positively correlated with apparent annual survival in the subsequent year, suggesting that the effects of winter precipitation carried over to influence survival probability of individuals in later seasons. Projection modeling revealed that a decrease in Bahamas March rainfall >12.4% from its current mean could result in negative population growth in this species. Collectively, our results suggest that increased drought during the non-breeding season, which is predicted to occur under multiple climate change scenarios, could have important consequences on the annual survival and population growth rate of Kirtland's warbler and other Neotropical-Nearctic migratory bird species.

Demographic drivers of decline and recovery in an Afro-Palaearctic migratory bird population.

Across Europe, rapid population declines are ongoing in many Afro-Palaearctic migratory bird species, but the development of appropriate conservation actions across such large migratory ranges is severely constrained by lack of understanding of the demographic drivers of these declines. By constructing regional integrated population models (IPMs) for one of the suite of migratory species that is declining in the southeast of Britain but increasing in the northwest, we show that, while annual population growth rates in both regions vary with adult survival, the divergent regional trajectories are primarily a consequence of differences in productivity. Between 1994 and 2012, annual survival and productivity rates ranged over similar levels in both regions, but high productivity rates were rarer in the declining southeast population and never coincided with high survival rates. By contrast, population growth in the northwest was fuelled by several years in which higher productivity coincided with high survival rates. Simulated population trajectories suggest that realistic improvements in productivity could have reversed the decline (i.e. recovery of the population index to more than or equal to 1) in the southeast. Consequently, actions to improve productivity on European breeding grounds are likely to be a more fruitful and achievable means of reversing migrant declines than actions to improve survival on breeding, passage or sub-Saharan wintering grounds.

PSS15 - Budget Impact of Apremilast for Moderate to Severe Plaque Psoriasis in the UK

Apremilast is an orally administered, small-molecule phosphodiesterase-4 inhibitor. It has a novel mechanism of action, targeting multiple steps implicated in the pathogenesis of psoriasis. Apremilast was approved by the European Medicines Agency in 2015 for the treatment of moderate-to-severe chronic plaque psoriasis (PsO) in adult patients who failed to respond to or have a contraindication to, or are intolerant to other systemic therapies. We assessed the budget impact of introducing apremilast in the current treatment portfolio for psoriasis from the UK payer perspective. A 5-year budget impact model was developed using a prevalence-based approach. The target population was estimated based on the total UK population, annual population growth rate, prevalence of PsO, and proportion of patients with moderate-to-severe disease. The total psoriasis population was divided into 3 categories: untreated patients, patients receiving ≥1 conventional systemic non-biologic therapy (SNBT), and patients on biologics. Biologic treatments included adalimumab, etanercept, infliximab, secukinumab, and ustekinumab. Biosimilars for etanercept and infliximab were also considered. Drug costs were quoted from the British National Formulary (BNF) and the Monthly Index of Medical Specialties (MIMS). Administration costs were obtained from the National Clinical Guideline Centre (NCGC); physician visit and laboratory test costs were informed by National Health Service (NHS) reference costs, the NCGC, and literature values. Over a 5-year period, the number of patients treated with apremilast was estimated to increase from 69 to 1,980. Inclusion of apremilast decreased the total budget by 2.19% (£735,221,377 vs. £751,645,055) relative to the world without. In the final year, drug acquisition costs decreased by 4.43% (£124,099,644 vs. £129,856,022), administration costs by 18.67% (£671,543 vs. £825,667), and monitoring costs by 2.81% (£21,291,886 vs. £21,907,514), yielding a net cost saving of 4.28%. Inclusion of apremilast in the PsO treatment regimen in the UK was cost saving in all respects

Higher Education Institutions and Regional Growth: The Case of New Zealand

We examine the relationship between the presence of Higher Education Institutions (HEIs) and local growth, using a sample of 57 New Zealand Territorial Local Authorities (TLAs) between 1986 and 2013. Our models include a large set of controls, including past growth. An innovation of our approach is that we include official population projections as a control to account for growth-related factors that were perceived at the time by policy makers, but are otherwise unobservable to the econometrician. Holding all else equal, we find that a greater university share of Equivalent Full Time Students (EFTS) to working-age population raises population and employment growth. At the means, a one percentage point increase in university EFTS share is associated with a 0.19 (0.14) percentage point increase in the annual average population (employment) growth rate. This relationship holds under all alternative specifications, including different HEI activity definitions, samples, and specifications. On the other hand, growth related to polytechnic activity was estimated less precisely, and is much smaller. While our results suggest a positive association between university activity and growth, we find no evidence for complementarities between HEI activity and several indicators of urbanisation and innovation, nor do we find evidence that HEI presence affected the industrial (sectoral) structure of the local economy.

You can hide but you can't run: apparent competition, predator responses and the decline of Arctic ground squirrels in boreal forests of the southwest Yukon.

Throughout much of North America’s boreal forest, the cyclical fluctuations of snowshoe hare populations (Lepus americanus) may cause other herbivores to become entrained in similar cycles. Alternating apparent competition via prey switching followed by positive indirect effects are the mechanisms behind this interaction. Our purpose is to document a change in the role of indirect interactions between sympatric populations of hares and arctic ground squirrels (Urocitellus parryii plesius), and to emphasize the influence of predation for controlling ground squirrel numbers. We used mark-recapture to estimate the population densities of both species over a 25-year period that covered two snowshoe hare cycles. We analysed the strength of association between snowshoe hare and ground squirrel numbers, and the changes to the seasonal and annual population growth rates of ground squirrels over time. A hyperbolic curve best describes the per capita rate of increase of ground squirrels relative to their population size, with a single stable equilibrium and a lower critical threshold below which populations drift to extinction. The crossing of this unstable boundary resulted in the subsequent uncoupling of ground squirrel and hare populations following the decline phase of their cycles in 1998. The implications are that this sustained Type II predator response led to the local extinction of ground squirrels. When few individuals are left in a colony, arctic ground squirrels may also have exhibited an Allee effect caused by the disruption of social signalling of approaching predators.

City profile: Tamale, Ghana

Tamale is the capital of the Northern Region of Ghana. It emerged as a growth point for northern Ghana upon independence in 1957, and has since become the third largest urban centre in the country. The city has the second highest annual population growth rates after Kumasi Metropolitan Area. In this paper, we profile Tamale regarding its social, economic and spatial growth dynamics, transformation and governance as well as highlight the implications of the city's growth trajectories for its sustainable futures.