Ella Tsahar

Distribution and Extinction of Ungulates during the Holocene of the Southern Levant

Background The southern Levant (Israel, Palestinian Authority and Jordan) has been continuously and extensively populated by succeeding phases of human cultures for the past 15,000 years. The long human impact on the ancient landscape has had great ecological consequences, and has caused continuous and accelerating damage to the natural environment. The rich zooarchaeological data gathered at the area provide a unique opportunity to reconstruct spatial and temporal changes in wild species distribution, and correlate them with human demographic changes. Methodology Zoo-archaeological data (382 animal bone assemblages from 190 archaeological sites) from various time periods, habitats and landscapes were compared. The bone assemblages were sorted into 12 major cultural periods. Distribution maps showing the presence of each ungulate species were established for each period. Conclusions The first major ungulate extinction occurred during the local Iron Age (1,200–586 BCE), a period characterized by significant human population growth. During that time the last of the largest wild ungulates, the hartebeest (Alcelaphus buselaphus), aurochs (Bos primigenius) and the hippopotamus (Hippopotamus amphibius) became extinct, followed by a shrinking distribution of forest-dwelling cervids. A second major wave of extinction occurred only in the 19th and 20th centuries CE. Furthermore, a negative relationship was found between the average body mass of ungulate species that became extinct during the Holocene and their extinction date. It is thus very likely that the intensified human activity through habitat destruction and uncontrolled hunting were responsible for the two major waves of ungulate extinction in the southern Levant during the late Holocene.

Dietary protein influences the rate of 15N incorporation in blood cells and plasma of Yellow-vented bulbuls (Pycnonotus xanthopygos).

SUMMARY The rate at which an animals tissues incorporate the isotopic composition of food determines the time window during which ecologists can discern diet changes. We investigated the effect of protein content in the diet on the incorporation rate of 15N into the plasma proteins and blood cells of Yellow-vented bulbuls (Pycnonotus xanthopygos). Using model comparison analyses, we found that one-compartment models described incorporation data better than two-compartment models. Dietary protein content had a significant effect on the residence time of 15N in plasma proteins and blood cells. The diet with the highest protein content led to a 15N retention time of 21 and 5 days for cells and plasma, respectively. In contrast, average 15N retention time in the cells and plasma of birds fed on the diet with the lowest protein was 31 and 7 days, respectively. The isotopic discrimination factorΔ 15N=δ15Ntissues–δ15Ndiet was also dependent on dietary protein content, and was lowest in birds fed the diet with the highest protein content. Blood, plasma and excreta were enriched in 15N relative to diet. In contrast, ureteral urine was either significantly depleted of 15N in birds fed the diet with the lowest protein content or did not differ in δ15N from the diets with the intermediate and high protein content. Thus, isotopic incorporation rates and tissue-to-diet discrimination factors cannot be considered fixed, as they depend on diet composition.

Hummingbirds arrest their kidneys at night: diel variation in glomerular filtration rate in Selasphorus platycercus.

SUMMARY Small nectarivorous vertebrates face a quandary. When feeding, they must eliminate prodigious quantities of water; however, when they are not feeding, they are susceptible to dehydration. We examined the role of the kidney in the resolution of this osmoregulatory dilemma. Broad-tailed hummingbirds (Selasphorus platycercus) displayed diurnal variation in glomerular filtration rate (GFR). During the morning, midday and evening, GFRs were 0.9±0.6, 1.8±0.4 and 2.3±0.5 ml h–1, respectively. At midday, GFR increased linearly with increased water intake. During the evening, hummingbirds decreased renal fractional water reabsorption linearly with increased water intake. Broad-tailed hummingbirds appeared to cease GFR at night (–0.1±0.2 ml h–1) and decreased GFR in response to short-term (∼1.5 h) water deprivation. GFR seems to be very responsive to water deprivation in hummingbirds. Although hummingbirds and other nectarivorous birds can consume astounding amounts of water, a phylogenetically explicit allometric analysis revealed that their diurnal GFRs are not different from the expectation based on body mass.

DO NECTAR- AND FRUIT-EATING BIRDS HAVE LOWER NITROGEN REQUIREMENTS THAN OMNIVORES? AN ALLOMETRIC TEST

Abstract We used an allometric approach to compare the minimum nitrogen requirements (MNR) and the total endogenous nitrogen loss (TENL) of nectar- and fruit-eating birds with those of omnivorous birds. These two parameters were 4× higher in omnivores than in nectarivores and frugivores. In nectarivorous-frugivorous birds, MNR was 152.8 mg N kg−0.76 day−1; in omnivorous birds, it was 575.4 mg N kg−0.76 day−1. Similarly, TENL was 54.1 mg N kg−0.69 day−1 in nectarivores-frugivores, and 215.3 mg N kg−0.69 day−1 in omnivores. The residuals of the allometric relationships between TENL and MNR and body mass were positively correlated, which suggests that a large proportion of the interspecific variation in MNR is explained by variation in TENL. Although our results show that nectar- and fruit-eating birds have low nitrogen requirements, the mechanisms that these animals use to conserve nitrogen remain unclear. ¿Tienen las Aves Nectrarívoras y Frugívoras Requerimientos de Nitrógeno Menores que las Omnívoras? Una Prueba Alométrica

Are the Low Protein Requirements of Nectarivorous Birds the Consequence of Their Sugary and Watery Diet? A Test with an Omnivore

Nectar‐feeding birds have remarkably low nitrogen requirements. These may be due either to adaptation to a low‐protein diet or simply to feeding on a fluid diet that minimizes metabolic fecal nitrogen losses. We measured minimal nitrogen requirements (MNR) and total endogenous nitrogen loss (TENL) in the omnivorous European starling Sturnus vulgaris, fed on an artificial nectar‐like fluid diet of varying concentrations of sugar and protein. The MNR and TENL of the birds were similar and even slightly higher than allometrically expected values for birds of the starlings’ mass (140% and 103%, respectively). This suggests that the low measured nitrogen requirements of nectar‐feeding birds are not simply the result of their sugary and watery diets but a physiological adaptation to the low nitrogen input. We also measured the effect of water and protein intake on the nitrogenous waste form in the excreta and ureteral urine in European starlings. Neither high water intake nor low protein intake increased the fraction of nitrogen excreted as ammonia. Ammonia was excreted at consistently low levels by the starlings, and its concentration was significantly higher in ureteral urine than in excreta. We hypothesize that ureteral ammonia was reabsorbed in the lower intestine, indicating a postrenal modification of the urine.

SECONDARY METABOLITE EMODIN INCREASES FOOD ASSIMILATION EFFICIENCY OF YELLOW-VENTED BULBULS (PYCNONOTUS XANTHOPYGOS)

Abstract We studied the effect of the secondary metabolite emodin on food intake, food assimilation mass coefficient (AMC), feeding bout rate, and defecation rate in a frugivorous bird, the Yellow-vented Bulbul (Pycnonotus xanthopygos). Emodin is found in the ripe fruits of Mediterranean buckthorn (Rhamnus alaternus), which is commonly eaten by P. xanthopygos. Emodin (0.005 and 0.01% wet mass) increased dry matter AMC by 8–10% after isolating the effect of food intake. At a concentration of 0.001%, emodin increased the AMC of nitrogen, fat, and organic remains (mainly carbohydrates and proteins). Apart from emodin, fruits of R. alaternus contain a variety of secondary metabolites that may interact with each other and influence bird digestion. Artificial food laced with crude Rhamnus fruit extract increased food intake and dry matter AMC. Emodin (0.01% wet mass) increased the average time between defecations, but did not affect the time interval between feeding bouts nor the average amount consumed per feeding bout. We speculate that emodin increases food retention time. Longer retention time may explain the observed increase in AMC. Our results suggest that sometimes secondary metabolites in ripe fruit may not be detrimental to frugivores and the presence of emodin in the pulp of ripe buckthorn fruits might be selectively adaptive to the plant.

Cats in recent Chinese study on cat domestication are commensal, not domesticated

Recent archaeological research in China is rewriting the story of the origins of agriculture and plant and animal domestication. The study by Hu et al. (1) presents findings regarding early cat–human interactions with implications for domestication unearthed in Middle-Late Yangshao (6,000–5,000 B.P.) cultural levels at the site of Quanhucun, Shaanxi Province in the context of early Chinese Neolithic agriculture. Evidence provided by the authors includes morphometric, isotopic, and carbon-14 analyses of the cat skeletal remains.

Mammalian extinction in ancient Egypt, similarities with the southern Levant

Yeakel et al. (1) find that wild mammal extinction in ancient Egypt during the Holocene was nonrandom and coincided with abrupt climatic changes and a local cultural collapse. The authors provide compelling evidence that the deterioration of the natural Egyptian ecosystem gradually progressed during the Holocene. The extinction patterns provided vividly show that decreasing predator and prey (ungulates) diversity mirror increased desertification, human population growth, and political instability. We see strong ecological logic in Yeakel et al.’s (1) scenario and point to the advantages of conducting detailed comparisons of local extinction data to illuminate particularities and to better fine-tune broader hypotheses concerning Holocene extinctions.