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Speeded enumeration of visual objects typically produces fast and accurate performance for up to 3 to 4 items (subitization) but slower and less accurate performance thereafter (counting). We investigated enumeration ability in patients with Alzheimer's disease (AD) and in age-matched controls. AD patients were slower overall than controls. The subitizing span was significantly reduced in AD patients compared with controls (2.3 vs 3.5 items) and counting rate was significantly slower (451 vs 349 ms/item). Error rates were similar in the two groups except at numerosity 3, when AD patients made errors but controls did not (consistent with their subitizing spans). Within the AD patient group, several aspects of performance correlated significantly with Mini-Mental State Examination scores. Together, the results provide a striking contrast with studies showing preservation of enumeration ability in normal aging.

Until around 2000, giraffe Giraffa camelopardalis were believed to have no social structure. Despite a resurgence of interest in giraffe behaviour in around 2010, most studies are of isolated populations, making it difficult to draw general conclusions. Although it is now well established that giraffe social organisation is non‐random, there is little consensus as to what influences preferred and avoided associations or the underpinning mechanisms.We test two hypotheses: first, giraffe have a complex cooperative social system, exhibited by 1) stable groups of females, 2) offspring that stay in their natal group for part or all of their lives, 3) support by non‐mothers in rearing young, and 4) non‐reproductive females in the group; and second, giraffe form matrilineal societies, evidenced by 1) male dispersal, 2) female philopatry, 3) assistance in raising or protecting offspring, and 4) individual benefits gained from social foraging.We reviewed 404 papers on giraffe behaviour and social organisation; captive studies were included where they supplemented information from free‐living populations.We show that giraffe exhibit many of the features typical of mammals with complex cooperative social systems and matrilineal societies. However, the social complexity hypothesis posits that such species also require complex communication systems to regulate interactions and relations among group members; giraffe communication systems are poorly understood.Quantifying the fitness and survival benefits of the giraffe's social organisation is necessary to ensure its long‐term survival. Giraffe numbers have declined by 40% since 1985, they have been declared extinct in seven (possibly nine) countries and are listed as Vulnerable by the International Union for Conservation of Nature. We identify research areas that will advance our understanding of giraffe behaviour and conservation requirements. [ABSTRACT FROM AUTHOR]

Giraffe populations have suffered a 40% decline in the past thirty years, making them a new priority for conservation and there are considerable uncertainty and disagreement over the taxonomic classification of giraffes. Consequently, there has never been a more critical time to fully understand the global population size and distribution of all giraffe subspecies. The Rothschild's giraffe Giraffa camelopardalis rothschildi (Linnaeus, 1758) is arguably one of the most imperilled giraffe subspecies. Once widespread across southern Sudan, Uganda and Kenya, the Rothschild's giraffe is now confined to a few, isolated and enclosed populations throughout Kenya and Uganda, with only one natural population remaining. Information about Rothschild's giraffe population size, distribution, and conservation history is patchy, and confined to recondite or inaccessible resources. Here, I present a review of taxonomy, distribution, conservation status and population size of the Rothschild's giraffe and present the most recent estimate of population sizes based on direct census data. Although the Latin name affixed to Rothschild's giraffe is subject to discussion, continued reference to this subspecies as G. c. rothschildi is strongly recommended. [ABSTRACT FROM AUTHOR]

The article focuses on color variations in giraffes. It presents a case of progressive coat depigmentation observed in an adult male giraffe. It is said that all giraffes have a pale base color overlaid with irregularly shaped patches of brown or orange, however, there may be some variation between subspecies.

The article presents a study which examines the behaviour of giraffe mothers after the death of their calves. The authors of the study observed Rothschild's giraffes in Soysambu Conservancy, Kenya and Masai giraffes in Serengeti National Park in Tanzania. It reveals that each observed mother remained near the site of death calves for three to four consecutive days.