Main Proximate Cause Research Articles

Where did the forest go? Post-deforestation land use dynamics in the Dry Chaco region in Northwestern Argentina

Land transformation is a major component of global change, directly altering habitat composition and spatial configuration, biodiversity, and ecosystem functioning. Over the last decades, the Dry Chaco region in Northwestern Argentina has become one of the regions most heavily transformed worldwide due to the expansion of its agricultural frontier. Many questions remain unanswered about how this process of change occurred. In this study, a parcel-scale database was used to assess the conversion of natural landscapes to different agroecosystems. The magnitude and direction of land use transitions during the last 20 years (2001–2019) were analyzed. Ranching is the main proximate cause of deforestation, accounting for more than 63% of the area cleared annually, though the land use expansion pattern has varied in space and time. Trajectories of land use transitions revealed a spatial arrangement where croplands have displaced ranching to drier areas. The analysis of the intensity of these transitions has shown that the trajectory of post-deforestation land use dynamics has followed a permanent systematic spatio-temporal pattern of change: (1) Dry Forest to Pastures; (2) Pastures to Single Crops; and (3) Single Cropping and Double Cropping systems, where processes of expansion, replacement, and intensification have been identified. Information on transition patterns has allowed us to develop a deeper understanding of land transformation processes, essential in the design of effective land use management strategies.

Breeding ecology of Eurasian bullfinches Pyrrhula pyrrhula in an Iberian hedgerow habitat

ABSTRACT The breeding ecology of the Iberian subspecies of the Eurasian bullfinch, Pyrrhula pyrrhula iberiae, is addressed for the first time. The studied population occupied a hedgerow habitat in northwestern Spain. Individuals directly watched in the study area and details of these sightings were recorded over a six-year period, and a total of 56 nests were monitored. The earliest date of nest building was within 11–30 April for all years. Fledglings were recorded leaving the nest during all the ten-day periods from the end of May to mid-August. Nest attendance, from the early building stage to when nestlings were ready to leave the nest, lasted approximately 36 days. The overall mean clutch size was 4.56 eggs. Clutch size decreased significantly at the end of the breeding season. For all egg traits, the minimum values for standard deviation were obtained in the intra-clutch analysis, and egg length was more variable than width. Nesting success increased progressively from April–May to June–July and August. The main proximate cause of nest failure was egg desertion/predation, followed by nest desertion during nest building and nestling desertion/predation. Mammals were the main agents in nests where the probable predator could be identified. Approximately half of the eggs became fledglings leaving the nest, no significant seasonal differences being observed for this parameter. In August, the ratio of juveniles to adults was 2.5–4.1, juveniles representing approximately 70–80% of the individuals seen and identified that month. The absence of significant interannual variation in important reproductive parameters could have been due to lack of interannual variation in the availability of food resources. Compared to other subspecies, mean clutch size of Iberian bullfinches is the smallest recorded in the western Palearctic, and they showed an earlier start to the breeding season and shorter mean egg length than North European and Russian populations.

Back to the Future: A Glance Over Wolf Social Behavior to Understand Dog-Human Relationship.

Simple SummaryWolves, the ancestors of dogs, are one of the most cooperative canine species. This cooperative propensity derives from the fact that each subject needs other group members to obtain resources and increase survival. The pack functions as a unit in which each individual collaborates in territory defence, hunting, and rearing of offspring. For this reason, even though a clear hierarchy exists among wolves, subordinates can provide help to dominants to obtain social tolerance in a sort of commodity exchange. Wolves can make peace after aggression, console victims of a conflict, and calm down the aggressors. This set of behaviors, also called post-conflict strategies, requires a social attentiveness towards others’ emotional state and the ability to coordinate appropriate reactions. Adult wolves also play. They engage in play fighting, which strongly resembles real fighting, by finely modulating their motor actions and quickly interpreting playmates’ intentions, thus maintaining the non-serious playful mood. All these cognitive and social skills were a fertile ground for the artificial selection operated by humans to redirect the cooperative propensity of wolves towards dog–human affective relationship.This review focuses on wolf sociobiology to delineate the traits of cooperative baggage driven by natural selection (wolf-wolf cooperation) and better understand the changes obtained by artificial selection (dog-human cooperation). We selected some behaviors of the dog’s ancestors that provide the basis for the expression of a cooperative society, such as dominance relationships, leverage power, post-aggressive strategies, and playful dynamics between pack members. When possible, we tried to compare the data on wolves with those coming from the dog literature. Wolves can negotiate commodities when the interacting subjects occupy different ranking positions by bargaining social tolerance with helping and support. They are able to manage group disruption by engaging in sophisticated post-conflict maneuvers, thus restoring the relationship between the opponents and reducing the spreading of aggression in the group. Wolves engage in social play also as adults to manipulate social relationships. They are able to flexibly adjust their playful interactions to minimize the risk of escalation. Complex cognitive abilities and communicative skills are probably the main proximate causes for the evolution of inter-specific cooperation in wolves.

Vanished Wars of Australia: the Archeological Invisibility of Aboriginal Collective Conflicts

"In the debate concerning the existence of collective armed conflict before the advent of agriculture and the emergence of wealth differentiation, Australia—a continent entirely occupied by economic egalitarian foragers until the end of the eighteenth century—provides key insights. We explore the ethnographic data, striving to build a comprehensive database of the collective fights which were recorded. This survey brings a total of 165 events, among which 32 display a comparatively high level of lethality, with ten killed or more, a proportion far from negligible. An examination of each testimony leads to the conclusion that they are, as a whole, likely reliable. We then briefly discuss the nature of these collective conflicts, which purposes are marked by the lack of wealth in Aboriginal societies: the two main proximate causes, by far, are rights over women and retaliation for real or supposed aggressions—notably, conflicts over territories and resources are almost absent. It is also argued that at least some of these conflicts should be qualified as “wars”. Finally, we show why those conflicts leave so few archeological remains, by dealing with art, bones, and material means of conflicts, with a special attention to the “hunting versus war” weapon question. We conclude that if in such technical and social circumstances, these events are fairly difficult to record ethnologically, they are almost (if not totally) invisible archeologically." (source editeur)

Institutional analysis of causes of deforestation in REDD+ pilot sites in the Equateur province: Implication for REDD+ in the Democratic Republic of Congo

As DRC moves from REDD+ readiness to implementation, analysis of the causes of deforestation at the local level is paramount. The present study contributes to this by assessing both proximate and underlying causes of deforestation in two REDD+ pilots of the Équateur province. The study found that agricultural expansion through shifting cultivation is the main proximate cause of deforestation. This activity is accelerated by logging that simplifies clearing of land. Logging also contributes to the total biomass loss from the forest. Shifting cultivation is driven by the poverty conditions of the study area. Poverty is also linked to the political and institutional structures of forest governance. These structures are controlled by political elites who influence local decisions to clear forests. While actions to curb deforestation might be challenging, this study suggests that addressing the underlying causes through effective land use planning and developing robust accountable institutions while providing alternative economic opportunities to the local population are necessary.

Long-Lived Termite Queens Exhibit High Cu/Zn-Superoxide Dismutase Activity.

In most organisms, superoxide dismutases (SODs) are among the most effective antioxidant enzymes that regulate the reactive oxygen species (ROS) generated by oxidative energy metabolism. ROS are considered main proximate causes of aging. However, it remains unclear if SOD activities are associated with organismal longevity. The queens of eusocial insects, such as termites, ants, and honeybees, exhibit extraordinary longevity in comparison with the nonreproductive castes, such as workers. Therefore, the queens are promising candidates to study the underlying mechanisms of aging. Here, we found that queens have higher Cu/Zn-SOD activity than nonreproductive individuals of the termite Reticulitermes speratus. We identified three Cu/Zn-SOD sequences and one Mn-SOD sequence by RNA sequencing in R. speratus. Although the queens showed higher Cu/Zn-SOD activity than the nonreproductive individuals, there were no differences in their expression levels of the Cu/Zn-SOD genes RsSOD1 and RsSOD3A. Copper (Cu2+ and Cu+) is an essential cofactor for Cu/Zn-SOD enzyme activity, and the queens had higher concentrations of copper than the workers. These results suggest that the high Cu/Zn-SOD activity of termite queens is related to their high levels of the cofactor rather than gene expression. This study highlights that Cu/Zn-SOD activity contributes to extraordinary longevity in termites.

A reversal of the socioeconomic gradient of nuptiality during the Swedish mid-20th-century baby boom

Research into the causes of the mid-20th-century baby boom has concluded that the main proximate cause of the fertility increase during the 1940s was earlier and more universal marriage in the cohorts born after 1910, and that this association between nupt

Exploration and recency as the main proximate causes of probability matching: a reinforcement learning analysis

Research has not yet reached a consensus on why humans match probabilities instead of maximise in a probability learning task. The most influential explanation is that they search for patterns in the random sequence of outcomes. Other explanations, such as expectation matching, are plausible, but do not consider how reinforcement learning shapes people’s choices. We aimed to quantify how human performance in a probability learning task is affected by pattern search and reinforcement learning. We collected behavioural data from 84 young adult participants who performed a probability learning task wherein the majority outcome was rewarded with 0.7 probability, and analysed the data using a reinforcement learning model that searches for patterns. Model simulations indicated that pattern search, exploration, recency (discounting early experiences), and forgetting may impair performance. Our analysis estimated that 85% (95% HDI [76, 94]) of participants searched for patterns and believed that each trial outcome depended on one or two previous ones. The estimated impact of pattern search on performance was, however, only 6%, while those of exploration and recency were 19% and 13% respectively. This suggests that probability matching is caused by uncertainty about how outcomes are generated, which leads to pattern search, exploration, and recency.

Prolonged stigma and flower lifespan in females of the gynodioecious plant Geranium sylvaticum

In gynodioecious plants females need a reproductive advantage over hermaphrodites to be maintained in the same population. Generally, three main proximate causes for a female advantage are considered: inbreeding avoidance, different resource allocation patterns, and differences in ecological interactions. A mechanism potentially causing a female advantage that is rarely discussed is a difference in floral longevity between the genders. Females may have a longer stigma lifespan than hermaphrodites, which can affect pollination. Stigma and flower lifespan are rarely documented in gynodioecious species, although it is a common observation in dioecious species that female plants flower longer than males. Here we focus on the stigma and flower lifespan of gynodioecious Geranium sylvaticum, which could potentially contribute to the female advantage observed in this and other closely related species. We measured the stigma and flower lifespan in unpollinated flowers of female, hermaphrodite and plants with an intermediate gender expression. Our results show that stigma lifespan is almost twice as long in females as in hermaphrodites and intermediate plants. Also flower lifespan is longest in females. We discuss the potential mechanisms through which an increased floral lifespan can lead to a female advantage despite the generally lower pollinator visitation rates observed in females by reviewing available studies. Our study shows that increased floral persistence in females can be an important aspect in the maintenance of females in gynodioecious plants and should be taken into account as a potential proximate cause for a female advantage.

Post‐fledging survival of altricial birds: ecological determinants and adaptation

For altricial young, fledging is an abrupt step into an unknown environment. Despite increasing numbers of studies addressing the post-fledging period, our current knowledge of the causes and consequences of post-fledging survival remains fragmentary. Here, we review the literature on post-fledging survival of juvenile altricial birds, addressing the following main questions: Is low post-fledging survival a bottleneck in the altricial reproductive cycle? What is known of proximate and ultimate causal factors such as trophic relations (food and predation), habitat conditions, or abiotic factors acting in the post-fledging period? We analyzed weekly survival estimates from 123 data series based on studies of 65 species, covering weeks 1–13 post-fledging. As a general pattern, survival of fledglings was low during the first week post-fledging (median rate = 0.83), and improved rapidly with time post-fledging (week 4 median rate = 0.96). For ground-nesting species, survival immediately after leaving nests was similar to egg-to-fledging survival. For species breeding above-ground, survival during the first week post-fledging was substantially lower than during both the nestling period and later post-fledging stages. Thus, the early post-fledging period is a bottleneck of markedly elevated mortality for most altricial species. Predation was the main proximate cause of mortality. Various factors such as habitat, annual and seasonal variation in the environment, and the physical condition of fledglings have been found to affect post-fledging survival. Individual survival depended strongly on physical traits such as mass and wing length, which likely influence the ability of fledglings to escape predation. Trophic relationships at various levels are the main ultimate driver of adaptation of traits relevant to survival during the pre- and post-fledging periods. Spatiotemporal dynamics of food resources determine the physical development of juveniles and, in turn, their performance after fledging. However, predators can cause quick and efficient selection for fledgling traits and adult breeding decisions. Parental strategies related to clutch size and timing of breeding, and the age and developmental stage at which young fledge have substantial effects on post-fledging survival. The intensity and duration of post-fledging parental investment also influences fledgling survival. Post-fledging mortality is therefore not a random and inevitable loss. Traits and strategies related to fledging and the post-fledging stage create large fitness differentials and, therefore, are integral, yet poorly understood, parts of the altricial reproductive strategy.

Acute Myeloid Leukemia: analysis of epidemiological profile and survival rate

ObjectiveTo describe the epidemiological profile and the survival rate of patients with acute myeloid leukemia (AML) in a state reference pediatric hospital. MethodClinical‐epidemiological, observational, retrospective, descriptive study. The study included new cases of patients with AML, diagnosed between 2004 and 2012, younger than 15 years. ResultsOf the 51 patients studied, 84% were white; 45% were females and 55%, males. Regarding age, 8% were younger than 1 year, 47% were aged between 1 and 10 years, and 45% were older than 10 years. The main signs/symptoms were fever (41.1%), asthenia/lack of appetite (35.2%), and hemorrhagic manifestations (27.4%). The most affected extra‐medullary site was the central nervous system (14%). In 47% of patients, the white blood cell (WBC) count was below 10,000/mm3 at diagnosis. The minimal residual disease (MRD) was less than 0.1%, on the 15th day of treatment in 16% of the sample. Medullary relapse occurred in 14% of cases. When comparing the bone marrow MRD with the vital status, it was observed that 71.42% of the patients with type M3 AML were alive, as were 54.05% of those with non‐M3 AML. The death rate was 43% and the main proximate cause was septic shock (63.6%). ConclusionsIn this study, the majority of patients were male, white, and older than 1 year. Most patients with WBC count<10,000/mm3 at diagnosis lived. Overall survival was higher in patients with MRD<0.1%. The prognosis was better in patients with AML‐M3.

Acute Myeloid Leukemia: analysis of epidemiological profile and survival rate

ObjectiveTo describe the epidemiological profile and the survival rate of patients with acute myeloid leukemia (AML) in a state reference pediatric hospital. MethodClinical–epidemiological, observational, retrospective, descriptive study. The study included new cases of patients with AML, diagnosed between 2004 and 2012, younger than 15 years. ResultsOf the 51 patients studied, 84% were white; 45% were females and 55%, males. Regarding age, 8% were younger than 1 year, 47% were aged between 1 and 10 years, and 45% were older than 10 years. The main signs/symptoms were fever (41.1%), asthenia/lack of appetite (35.2%), and hemorrhagic manifestations (27.4%). The most affected extra-medullary site was the central nervous system (14%). In 47% of patients, the white blood cell (WBC) count was below 10,000/mm3 at diagnosis. The minimal residual disease (MRD) was less than 0.1%, on the 15th day of treatment in 16% of the sample. Medullary relapse occurred in 14% of cases. When comparing the bone marrow MRD with the vital status, it was observed that 71.42% of the patients with type M3 AML were alive, as were 54.05% of those with non-M3 AML. The death rate was 43% and the main proximate cause was septic shock (63.6%). ConclusionsIn this study, the majority of patients were male, white, and older than 1 year. Most patients with WBC count <10,000/mm3 at diagnosis lived. Overall survival was higher in patients with MRD <0.1%. The prognosis was better in patients with AML-M3.

Why Have Divorce Rates Fallen?: The Role of Women’s Age at Marriage

American divorce rates rose from the 1950s to the 1970s peaked around 1980, and have fallen ever since. The mean age at marriage also substantially increased after 1970. I explore the extent to which the rise in age at marriage can explain the decrease in divorce rates for cohorts marrying after 1980 using data from the Survey of Income and Program Participation, 1979 National Longitudinal Survey of Youth, and National Survey of Family Growth. Three different empirical approaches suggest that the increase in women’s age at marriage is the main proximate cause of the fall in divorce rates.

Proximate and underlying causes of forest cover change in Peninsular Malaysia

This study examined the process and causes of forest cover change in Peninsular Malaysia from 1970 to 2010. Time series data on forest cover, land use, timber production, and socio-economic variables of Peninsular Malaysia were analyzed by regression modeling using Akaike Information Criterion (AIC). Peninsular Malaysia experienced extensive deforestation during the 1970s and early 1980s, but since then deforestation has slowed down substantially. Regression results highlighted that poverty alleviation was the principal underlying factor leading to change in forest area. Neither population growth nor economic growth was a major factor affecting forest cover. Oil palm expansion was identified as the main proximate cause of deforestation. Regression results also indicate that oil palm expansion greatly contributed to poverty reduction. Our empirical evidence suggests that in Peninsular Malaysia, agricultural development to reduce poverty, in particular oil palm development, initially led to deforestation. However, substantial decrease in poverty caused decrease in deforestation over the long term. Based on the results of this study, we propose poverty alleviation as a strategy to reduce deforestation. Our findings demonstrate the need to analyze factors that reduce deforestation and to develop effective REDD programs.

Sex and life stage dependent phototactic response of the marine copepod Calanus finmarchicus (Copepoda: Calanoida)

Irradiance thresholds for phototactic response were determined for the marine calanoid copepod Calanus finmarchicus (Gunnerus). C. finmarchicus is one of many zooplankton species that exhibit diel vertical migration. Light is considered the main proximate cause of diel vertical migration, but irradiance sensitivity is unknown for many ecologically important zooplankton taxa, including C. finmarchicus. Here we studied phototaxis in C. finmarchicus in response to low levels of irradiance using a custom-made experimental setup under controlled laboratory conditions. The setup consisted of an aquarium with a light stimulus in one end of a raceway. A video camera and near-infrared light for illumination were applied to monitor the response to light in the horizontal plane. Low levels of irradiance were achieved using a white LED and a combination of absorptive neutral density filters and diode pulsing.Stage V copepodites and adult females displayed negative phototaxis, and the threshold for phototactic response was 9.8×10−6μmolphotonsm−2s−1. Adult males displayed positive phototaxis and the corresponding threshold value was 9.9×10−7μmolphotonsm−2s−1. The results from the experiments were used to estimate the depths at which phototaxis is elicited in natural light conditions by conducting light simulations for an ocean scenario and a fjord scenario during peak spring bloom conditions. The estimated depths for irradiances that elicit a phototactic response corresponded to approximate depths of 158–186m in the ocean scenario and 48–57m in the fjord scenario. These depths are within the range of depth distributions of C. finmarchicus reported for ocean and fjord populations.

Drivers of Wetland Conversion: a Global Meta-Analysis

Meta-analysis of case studies has become an important tool for synthesizing case study findings in land change. Meta-analyses of deforestation, urbanization, desertification and change in shifting cultivation systems have been published. This present study adds to this literature, with an analysis of the proximate causes and underlying forces of wetland conversion at a global scale using two complementary approaches of systematic review. Firstly, a meta-analysis of 105 case-study papers describing wetland conversion was performed, showing that different combinations of multiple-factor proximate causes, and underlying forces, drive wetland conversion. Agricultural development has been the main proximate cause of wetland conversion, and economic growth and population density are the most frequently identified underlying forces. Secondly, to add a more quantitative component to the study, a logistic meta-regression analysis was performed to estimate the likelihood of wetland conversion worldwide, using globally-consistent biophysical and socioeconomic location factor maps. Significant factors explaining wetland conversion, in order of importance, are market influence, total wetland area (lower conversion probability), mean annual temperature and cropland or built-up area. The regression analyses results support the outcomes of the meta-analysis of the processes of conversion mentioned in the individual case studies. In other meta-analyses of land change, similar factors (e.g., agricultural development, population growth, market/economic factors) are also identified as important causes of various types of land change (e.g., deforestation, desertification). Meta-analysis helps to identify commonalities across the various local case studies and identify which variables may lead to individual cases to behave differently. The meta-regression provides maps indicating the likelihood of wetland conversion worldwide based on the location factors that have determined historic conversions.

Land cover changes in the Lachuá region, Guatemala: patterns, proximate causes, and underlying driving forces over the last 50 years

Identifying the patterns of land cover change (LCC) and their main proximate causes and underlying driving forces in tropical rainforests is an urgent task for designing adequate management and conservation policies. The Lachua region maintains the largest lowland rainforest remnant in Guatemala, but it has been highly deforested and fragmented during the last decades. This is the first paper to describe the patterns of LCC and the associated political and socioeconomic factors in the region over the last 50 years. We estimated spatial and temporal variations in LCC from a random sample of 24 1-km2 landscape plots during three time periods (1962–1987, 1987–2006, and 2006–2011) and evaluated how they were related to some important proximate causes and underlying driving forces. During the study period, 55 % of forest cover disappeared, at an annual rate of 1.6 %. The deforestation rate increased from 0.6 % (during the first study period) to 2.8 % (last period), but there was very high spatial variation. Landscape plots located outside conservation areas and close to roads lost between 80 and 100 % of forest cover, whereas the forest cover in landscapes located within protected areas remained intact during the study period. The establishment of new human settlements, roads, and annual crops was the main proximate cause during the first period, but during the second and third periods, open areas were mainly created to establish cattle pastures. Because ~75 % of forest cover has disappeared outside the protected areas, the conservation of this biodiversity hot spot will depend on the expansion of protected areas, and the promotion of forest regrowth and alternative biodiversity-friendly land uses in the landscape matrix.

Policy options to reduce deforestation based on a systematic analysis of drivers and agents in lowland Bolivia

The reduction of tropical deforestation is of crucial importance for mitigating climate change and curbing the loss of biodiversity. In light of the current international efforts to reduce deforestation associated to REDD+, effective and efficient country-specific policy options need to be identified to make progress on the ground. Taking lowland Bolivia as an example, we propose a systematic approach to identify and discuss such policy options; this systematic approach can be applied to other tropical contexts with ongoing conversion of forests to agricultural uses. We begin with the distinction of three land use categories associated with the main proximate causes of deforestation in lowland Bolivia, viz. mechanized agriculture, small-scale agriculture and cattle ranching, each of them linked to typical agents. Based on a systematic analysis of spatial and socioeconomic criteria, we then estimate the potential of land use expansion and the likely costs of deforestation reduction in order to formulate suitable policy options for each of the three proximate causes of deforestation. Although mechanized agriculture caused more than half of deforestation in lowland Bolivia, we argue that cattle ranching activities, which contributed to 27% of deforestation between 1992 and 2004, should be targeted as a priority since its expansion threatens forests in many different locations and improvements could be achieved at relatively low costs. In this light, enforcing land use legislation, accompanied by strengthening institutions on national and local levels, constitute tasks of utmost importance.

Movement responses by wolves to industrial linear features and their effect on woodland caribou in northeastern Alberta

Woodland caribou (Rangifer tarandus caribou) populations are declining across most of their range. Predation by wolves (Canis lupus) is believed to be the main proximate cause of these declines. However, it has been hypothesized that recent forestry and energy sector activity in caribou range ultimately might have caused population declines by altering wolf-caribou relationships. We tested the hypothesis that industrial linear features influence wolf movements in woodland caribou range in northeastern Alberta, resulting in increased wolf-caused caribou mortalities close to these features. Using step selection functions (SSF) and observed vs. simulated wolf movement paths, we found that wolf movement was influenced by natural linear features (rivers and streams) throughout the year, possibly because they provide ease of travel and high prey abundance. Wolf movement was further influenced by industrial linear features, but use of these features differed depending on line- type and season. Wolves showed strong selection for steps closer to conventional seismic lines during the snow-free season. Likewise, observed wolf movement paths followed conventional seismic lines more closely than simulated paths during snow-free months. Use of seismic lines as movement corridors might result in wolves hunting in caribou-preferred habitats (bogs and fens) more frequently than they did historically, particularly in the snow-free season when most caribou mortalities occur. However, we found no evidence that caribou mortalities occurred closer to industrial linear features than did live caribou. We conclude that wolf use of seismic lines increases predation risk for caribou close to these features, resulting in caribou avoidance of linear developments and thus functional loss of otherwise suitable habitat for caribou.

Increased ROS Production: A Component of the Longevity Equation in the Male Mygalomorph, Brachypelma albopilosa

BackgroundThe diversity of longevities encountered in wildlife is one of the most intriguing problems in biology. Evolutionary biologists have proposed different theories to explain how longevity variability may be driven by bad genes expression in late life or by gene pleiotropic effects. This reflexion has stimulated, in the last ten years, an active research on the proximal mechanisms that can shape lifespan. Reactive oxygen species (ROS), i.e., the by-products of oxidative metabolism, have emerged as the main proximate cause of ageing. Because ROS are mainly produced by the mitochondria, their production is linked to metabolic rate, and this may explain the differences in longevity between large and small species. However, their implication in the sex difference in longevity within a species has never been tested, despite the fact that these differences are widespread in the animal kingdom.Methodology/Principal FindingsMitochondrial superoxide production of hemolymph immune cells and antioxidant and oxidative damages plasma levels were measured in adult male and female B. albopilosa at different ages. We found that female spiders are producing less mitochondrial superoxide, are better protected against oxidative attack and are then suffering less oxidative damages than males at adulthood.Conclusions/SignificanceIn tarantulas, once reaching sexual maturity, males have a life expectancy reduced to 1 to 2 years, while females can still live for 20 years, in spite of the fact that females continue to grow and moult. This study evidences an increased exposure of males to oxidative stress due to an increase in mitochondrial superoxide production and a decrease in hemolymph antioxidant defences. Such a phenomenon is likely to be part of the explanation for the sharp reduction of longevity accompanying male tarantula maturity. This opens several fundamental research roads in the future to better understand how reproduction and longevity are linked in an original ageing model.