Calf/female ratio and population dynamics of wild forest reindeer in relation to wolf and moose abundances in a managed European ecosystem

Background The alternative prey hypothesis describes the mechanism for apparent competition whereby the mortality of the secondary prey species increases (and population size decreases decreases) by the increased predation by the shared predator if the population size of the primary prey decreases. Apparent competition is a process where the abundance of two co-existing prey species are negatively associated because they share a mutual predator, which negatively affects the abundance of both prey Here, we examined whether alternative prey and/or apparent competition hypothesis can explain the population dynamics and reproductive output of the secondary prey, wild forest reindeer (Rangifer tarandus fennicus) in Finland, in a predator-prey community in which moose (Alces alces) is the primary prey and the wolf (Canis lupus) is the generalist predator. Methods We examined a 22-year time series (1996–2017) to determine how the population size and the calf/female ratio of wild forest reindeer in Eastern Finland were related to the abundances of wolf and moose. Only moose population size was regulated by hunting. Summer predation of wolves on reindeer focuses on calves. We used least squares regression (GLS) models (for handling autocorrelated error structures and resulting pseudo-R2s) and generalized linear mixed (GLMs) models (for avoidance of negative predictions) to determine the relationships between abundances. We performed linear and general linear models for the calf/female ratio of reindeer. Results and synthesis The trends in reindeer population size and moose abundance were almost identical: an increase during the first years and then a decrease until the last years of our study period. Wolf population size in turn did not show long-term trends. Change in reindeer population size between consecutive winters was related positively to the calf/female ratio. The calf/female ratio was negatively related to wolf population size, but the reindeer population size was related to the wolf population only when moose abundance was entered as another independent variable. The wolf population was not related to moose abundance even though it is likely to consist the majority of the prey biomass. Because reindeer and moose populations were positively associated, our results seemed to support the alternative prey hypothesis more than the apparent competition hypothesis. However, these two hypotheses are not mutually exclusive and the primary mechanism is difficult to distinguish as the system is heavily managed by moose hunting. The recovery of wild forest reindeer in eastern Finland probably requires ecosystem management involving both habitat restoration and control of species abundances.

Females restrict the position of domatia and suffer more herbivory than hermaphrodites in Myriocarpa longipes, a neotropical facultative myrmecophyte

Domatia are hollow structures in plants occupied by ant colonies, in turn ants provide protection against herbivores. In plants, competition for resources has driven sex-related changes in the patterns of resource allocation to life-history traits and defence traits. The resource-competition hypothesis (RCH) proposes that female plants due to their higher investment in reproduction will allocate fewer resources to defence production, showing greater herbivore damage than other sexual forms. We hypothesise the existence of sex-related differences in defensive traits of domatia-bearing plants, being female plants less defended due to differences in domatia traits, such as size, number of domatia and their position, exhibiting more herbivore damage than hermaphrodite plants of Myriocarpa longipes, a facultative neotropical myrmecophyte. We found eight species of ants inhabiting domatia; some species co-inhabited the same plant, even the same branch. Our results are consistent with the predictions of RCH, as female plants had ant-inhabited domatia restricted to the middle position of their branches and exhibited greater herbivore damage in leaves than hermaphrodites. However, we did not find differences in domatia size and leaf area between sexual forms. Our study provides evidence for intersexual differences in domatia position and herbivory in a facultative ant–plant mutualism in M. longipes. We highlight the importance of considering the plant sex in ant–plant interactions. Differences in resource allocation related to sexual reproduction could influence the outcome of ant–plant interactions.

Temporal patterns in prey size between sexes in a raptor with extreme size dimorphism: testing the intersexual competition hypothesis using web-sourced photographs

In most vertebrates, males are larger than females. For raptors, sexual size dimorphism is reversed, with females being larger. Reversed sexual dimorphism (RSD) in raptors is strongly linked to diet, with species feeding on the most agile prey, for example bird-eating raptors, showing the greatest size differences between the sexes. Hypotheses for reversed sexual dimorphism (RSD) include the ‘intersexual competition’ hypothesis, which proposes that RSD evolved to enable pairs to expand their dietary niche (taking a wider range of prey sizes) during the nestling period when both sexes occupy and hunt within the same territory, and thereby reduce competition between the sexes. If intersexual competition is responsible for the evolution of RSD, we predict that sex-related differences in prey size and dietary niche breadth will be particularly pronounced during the nestling period (cf. the non-nestling period). We explore this prediction in the highly dimorphic Eurasian Sparrowhawk (Accipiter nisus), which displays the largest degree of RSD of all raptors, using web-sourced photographs to identify diet throughout the entire year. We analysed 666 photographs of sparrowhawks on their prey over time. In contrast to our predictions, sex-specific prey sizes were most similar during the nestling period compared to any other time of the year. Both males and females reduced the size of their prey during the nestling period which may be a result of the ‘ingestion rate’ hypothesis, or a strategy employed to prevent hunting-related injuries during this critical period of the year.

Did OPEC change its behaviour after the November 2014 meeting?

We analyse the behaviour of OPEC as a group by formulating a theoretical model that encompasses the perfect competition model and various forms of the imperfect competition model. By confronting the theoretical model with quarterly data for the period from 1992 to 2013 within the context of a cointegrated vector autoregressive (CVAR) model, we find support for the imperfect competition hypothesis regarding the output decisions of OPEC. We also find that a dynamic equilibrium correction model with imperfect competition is stable in-sample. However, a forecasting exercise for the period from 2014 to 2018 reveals that the model breaks down following the November 2014 meeting at which OPEC decided to keep its supply unchanged despite the huge oil price drop in advance. The model systematically underpredicts OPEC production over the forecast period and by as much as 2.5 million barrels per day at the end of 2016. During 2018, however, the model forecasts OPEC production quite well. Our findings suggest that the behaviour of OPEC did indeed change significantly after the November 2014 meeting.

Empathetic Factors and Influences on Physical Performance: A Topical Review

Performance is dependent upon both physical and psychological factors. As a social animal, human behaviors are influenced by interactions with others. Empathy is based on social interactions and is defined as the understanding, awareness of, sensitivity to, and ability to vicariously experience the feelings, thoughts, and experience of another. There are few investigations on the influence of empathy in relation to individual and team performance and activity. There is some initial research suggesting that observing sad photos or videos or fatiguing exercise can adversely affect subsequent performance. Possible mechanisms may be attributed to mirror neurons or the affordance competition hypothesis. The relative degree of empathetic influences can be modulated by sex, age, personal familiarity, cultures and other factors. With the limited research in sport and exercise science, there is a need for more research to investigate the role of empathy on individual and team performances. The objective of this topical review was to examine the possible effects of empathy on physical performance, the potential underlying mechanisms and influencing variables moderating the association between empathy and performance?

The dynamic competition hypothesis

We study competitive and negative interactions in real world social network in which nodes represent agents and edges appear over discrete time step. We consider directed social network of competing agents that evolve dynamically over time, where directed edges represent some kind of negative relationships between the agents in the social network. We present a novel hypothesis to identify the alliances and leaders within the the dynamic competition networks. We verify our hypothesis by using historical voting data of the social game shows Survivor and Big Brother.

The dynamic competition hypothesis

We study competitive and negative interactions in real world social network in which nodes represent agents and edges appear over discrete time step. We consider directed social network of competing agents that evolve dynamically over time, where directed edges represent some kind of negative relationships between the agents in the social network. We present a novel hypothesis to identify the alliances and leaders within the the dynamic competition networks. We verify our hypothesis by using historical voting data of the social game shows Survivor and Big Brother.

Political Budget Cycle, Tax Collection, and Yardstick Competition

This paper exploits the political cycle of Italian municipalities to test for the presence of strategic interactions in the collection of local taxation. The revenue from the personal income tax surcharge—a tax tool of low salience—is (positively) plagued by political manipulation and is found to be a strategic complement, but only when mayors run for re-election, a finding consistent with the yardstick competition hypothesis. More salient fiscal tools, such as property tax and user fees and charges, are also (negatively) affected by budget cycles, but they do not appear to be spatially correlated.

Does Neuronal Recycling Result in Destructive Competition? The Influence of Learning to Read on the Recognition of Faces

Written language, a human cultural invention, is far too recent a development for dedicated neural infrastructure to have evolved in its service. Newly acquired cultural skills, such as reading, thus recycle evolutionarily older circuits that originally evolved for different, but similar, functions (e.g., visual object recognition). The destructive-competition hypothesis predicts that this neuronal recycling has detrimental behavioral effects on the cognitive functions for which a cortical network originally evolved. In a study with 97 literate, low-literate, and illiterate participants from the same socioeconomic background, we found that even after adjusting for cognitive ability and test-taking familiarity, learning to read was associated with an increase, rather than a decrease, in object-recognition abilities. These results are incompatible with the claim that neuronal recycling results in destructive competition and are consistent with the possibility that learning to read instead fine-tunes general object-recognition mechanisms, a hypothesis that needs further neuroscientific investigation.