Variação sazonal na riqueza e na abundância de pequenos mamíferos, na estrutura da floresta e na disponibilidade de artrópodes em fragmentos florestais no Mato Grosso, Brasil

We captured small mammals in eight forest fragments (43 a 1.411 ha.) during the dry and wet seasons, in southwest Mato Grosso, Brazil, and investigated the variation in small mammal richness and abundance, as well as in forest structure variables (litter volume and canopy openness) and arthropod availability, between the two seasons. Sampling was carried out during the wet season between 2002 and 2003 and in the dry season of 2003. In each fragment, we used Sherman, Tomahawk, snap, and pitfall traps during 10 consecutive days per season, totaling 17,600 trap x nights. In total, we obtained 379 captures of 20 species, seven of marsupials and 13 of rodents. Overall capture success was 2.2% (1.6% during the wet season and 2.7% during the dry season). Total richness, richness of rodents, richness of marsupials, total abundance and abundance of rodents did not varied significantly between seasons. However, marsupial abundance was significantly lower in the dry season, when rainfall is high. Litter volume was significantly higher during the dry season, while arthropod availability was significantly higher during the wet season. Therefore, higher food availability during the wet season may have made trap baits less attractive. In general, the observed variations between dry and wet seasons are in accordance with patterns described in other studies

Temporal niche overlap among insectivorous small mammals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Being active in the same environment at different times exposes animals to the effects of very different environmental factors, both biotic and abiotic. In the present study, we used live traps equipped with timing devices to evaluate the potential role of biotic factors (competition and food abundance) on overall overlap in the temporal niche axis of 4 insectivorous small mammals in high-elevation grassland fields (campos de altitude) of southern Brazil. Based on resources availability (invertebrates), data on animal captures were pooled in 2 seasons: scarcity (June 2001September 2001) and abundance (November 2001May 2002) seasons. We tested for non-random structure in temporal niche overlap among the species in each season. These species were the rodents Oxymycterus nasutus (Waterhouse, 1837), Deltamys sp., Akodon azarae (Fischer, 1829), and the marsupial Monodelphis brevicaudis Olfers, 1818. The studied community was mainly diurnal with crepuscular peaks. Simulations using the Pianka index of niche overlap indicated that the empirical assemblage-wide overlap was not significantly different from randomly generated patterns in the abundance season but significantly greater than expected by chance alone in the scarcity season. All the species showed an increase in temporal niche breadth during the abundance season, which appears to be related to longer daylength and high nocturnal temperatures. Patterns on both temporal niche overlap and temporal niche breadth were the opposite to those that we were expecting in the case of diel activity patterns determined by competition for dietary resources. Therefore, we conclude that competition did not seem to be preponderant for determining patterns of temporal niche overlap by the studied community.64375386British Ecological Society [1841]UNISINOSFAPERGS [0112763]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)British Ecological Society [1841]FAPERGS [0112763]CNPq [300286/99-6

Seasonal patterns and influence of temperature on the daily activity of the diurnal neotropical rodent Necromys lasiurus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We investigated the relation between temperature and diel activity patterns of Necromys lasiurus (Lund, 1841) in 10 sites of open vegetation (grassland fields) in the Cerrado (savanna-like vegetation) of central Brazil. We used live traps equipped with timing devices during two trapping sessions: in the end of the dry season (session 1, October 2001) and in the wet season (session 2, January February 2002). Necromys lasiurus is basically a diurnal rodent with more pronounced crepuscular and nocturnal activity in the dry season than in the wet season. Only in the wet season did we detect significant between-gender differences, with males being less active than females in the first hours after sunrise but more active between 0900 and 1200. There was no significant activity temperature relation in the dry season, but in the wet season, both genders showed a positive relation between ambient temperature and activity. Individuals might be avoiding hot midday hours in the end of the dry season to minimize time exposure to a physiologically stressful condition caused by the joint action of high temperatures and extremely low relative humidity (<15%). In the rainy season, the high relative humidity (80%-90%) might allow the animals to show a positive relation between activity and ambient temperature.883259265Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [300286/99-6

ROTIV: RFID Ownership Transfer with Issuer Verification

RFID tags travel between partner sites in a supply chain. For privacy reasons, each partner “owns” the tags present at his site, i.e., the owner is the only entity able to authenticate his tags. However, when passing tags on to the next partner in the supply chain, ownership of the old partner is “transferred” to the new partner. In this paper, we propose ROTIV, a protocol that allows for secure ownership transfer against some malicious owners. Furthermore, ROTIV offers issuer verification to prevent malicious partners from injecting fake tags not originally issued by some trusted party. As part of ownership, ROTIV provides a constant-time, privacy-preserving authentication. ROTIV’s main idea is to combine an HMAC-based authentication with tag key and state updates during ownership transfer. To assure privacy, ROTIV implements tag state re-encryption techniques and key update techniques, performed on the reader. ROTIV is designed for lightweight tags – tags are only required to evaluate a hash function

New privacy results on synchronized RFID authentication protocols against tag tracing

Many RFID authentication protocols with randomized tag response have been proposed to avoid simple tag tracing. These protocols are symmetric in common due to the lack of computational power to perform expensive asymmetric cryptography calculations in low-cost tags. Protocols with constantly changing tag key have also been proposed to avoid more advanced tag tracing attacks. With both the symmetric and constant changing properties, tag and reader re-synchronization is unavoidable as the key of a tag can be made desynchronized with the reader due to offline attacks or incomplete protocol runs. In this paper, our contribution is to classify these synchronized RFID authentication protocols into different types and then examine their highest achievable levels of privacy protections using the privacy model proposed by Vaudenay in Asiacrypt 2007 and later extended by Ng et al. in ESORICS 2008. Our new privacy results show the separation between weak privacy and narrow-forward privacy in these protocols, which effectively fills themissing relationship of these two privacy levels in Vaudenay’s paper and answer the question raised by Paise and Vaudenay in ASIACCS 2008 on why they cannot find a candidate protocol that can achieve both privacy levels at the same time. We also show that forward privacy is impossible with these synchronized protocols