Season but not sex influences burrow length and complexity in the non-sexually dimorphic solitary Cape mole-rat (Rodentia : Bathyergidae)

Little is known about how environmental factors such as season influence burrowing activity, burrow structure or reproductive behaviour in subterranean mammals. We excavated burrow systems of male and female Georychus capensis, a solitary, subterranean rodent, in winter (wet season) and summer (dry season) to investigate whether any seasonal differences due to putative mate-seeking behaviour of males were apparent. Burrow structure did not differ between sexes, but did differ between seasons. For both sexes, summer burrows were shorter in length and covered a smaller area but explored the surrounding environment more efficiently than did winter burrows. Summer burrows had fewer mounds present indicating less expansion of the burrow systems in this season. We discuss these differences in exploration and use of the environment between seasons but not between sexes in terms of mating strategies of G. capensis and observed levels of sexual dimorphism in our populations. This study supports recent concepts regarding female competition and selection that may favour the expression of female exaggerated traits, which affect a female’s ability to acquire reproductive resources that often appear similar to that selected for by males.This research was supported by the University of Pretoria, by the SARChI Chair of Behavioural Ecology and Physiology and by the National Research Foundation, South Africa to NCB.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-7998hb2016Mammal Research InstituteZoology and Entomolog

Seasonal effects on digging activity and burrow architecture in the Cape dune mole-rat, Bathyergus suillus (Rodentia : Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement raising young. Instead, they invest indirectly in their own morphological and physiological attributes which enhance their chance of reproduction. Such secondary morphological sex traits may contribute to differences in the burrow architecture of fossorial mammals, such as the Cape dune mole-rat, Bathyergus suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the environment more efficiently than females. This is presumably because of the increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to dispose of soil onto the surface when the soil is less friable during the summer. Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment.University of Pretoria, by the SARChI Chair of Mammal Behavioural Ecology and Physiology and by the National Research Foundation, South Africa to N.C.B.http://africanzoology.journals.ac.za/am2013ab201

Seasonal changes in burrow geometry of the common mole rat (Rodentia: Bathyergidae)

Sociality in mole rats has been suggested to have evolved as a response to the widely dispersed food resources and the limited burrowing opportunities that result from sporadic rainfall events. In the most arid regions, individual foraging efficiency is reduced, and energetic constraints increase. In this study, we investigate seasonal differences in burrow architecture of the social Cryptomys hottentotus hottentotus in a mesic region. We describe burrow geometry in response to seasonal weather conditions for two seasons (wet and dry). Interactions occurred between seasons and colony size for the size of the burrow systems, but not the shape of the burrow systems. The fractal dimension values of the burrow systems did not differ between seasons. Thus, the burrow complexity was dependent upon the number of mole rats present in the social group.The University of Pretoria, by the SARChI Chair of Mammal Behavioural Ecology and Physiology and by the National Research Foundation, South Africa to NCB.http://link.springer.com/journal/114hj201

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Seasonal effects on digging activity and burrow architecture in the Cape dune mole-rat, Bathyergus suillus (Rodentia: Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement  raising young. Instead, they invest indirectly in their own morphological and  physiological attributes which enhance their chance of reproduction. Such  secondary morphological sex traits may contribute to differences in the burrow  architecture of fossorial mammals, such as the Cape dune mole-rat,  Bathyergus  suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow  configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the   environment more efficiently than females. This is presumably because of the  increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to  dispose of soil onto the surface when the soil is less friable during the summer.  Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment.Key words: burrow structure, seasonality, sexual selection, mate choice, energetics

Seasonal effects on digging activity and burrow architecture in the Cape dune mole-rat, Bathyergus suillus (Rodentia: Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement raising young. Instead, they invest indirectly in their own morphological and physiological attributes which enhance their chance of reproduction. Such secondary morphological sex traits may contribute to differences in the burrow architecture of fossorial mammals, such as the Cape dune mole-rat, Bathyergus suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the environment more efficiently than females. This is presumably because of the increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to dispose of soil onto the surface when the soil is less friable during the summer. Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment