Seasonal Shift

In the first week of December 2016, this investigation was carried out to determine the ecological border around Nijhum Dwip Island. During the investigation period, chosen stations 1-8(N 22 0 05′ 06.7″ E 91 0 01′ 58.8″ , N 22 0 06′ 07.2″ E 90 0 58′ 56.9″, N 22 0 03′ 18.1″ E 90 0 56′ 38.5″, N 22 0 01′ 37.6″ E 90 0 57′ 58.8″, N 22 0 05′ 00.8″ E 91 0 01′ 25.1″, N 22 0 03′ 44.6″ E 91 0 06′ 50.9″, N 22 0 04′ 38.8″E 91 0 05′ 55.9″, N 22 0 03′ 42.4″ E 91 0 02′ 25.2″) recorded air temperatures ranging from 24.1°C to 27.5°C. Significant correlations between air and water temperatures were seen, and daylight had an impact as well. During the study period, the stations' surface water temperatures varied from 25.1°C to 27°C. Throughout the research area, the pH values were largely constant. Between the locations, the pH of the surface water varied from 7.4 to 7.8. Between 3.70 ppt to 5.45 ppt, the salinity of the surface water reported at eight locations was low. Freshwater runoff from the lower Meghna Estuary may be the cause of this. From 5.20 to 8.20 mg/l of dissolved oxygen were found in surface water at stations 1 through 8. Normal estuarine biota will thrive in this environment. The research area's water transparency was very low. During the study period, the Secchi-Disc transparency varied across stations 1-8 from 4-15 cm. Between stations 1 and 8, the surface water's total dissolved solids (TDS) ranged from 575 to 709 mg/l.

Large plots of maize in agricultural landscapes are associated with reduced reproductive output of females and impaired population development of freeliving populations of European brown hares (Lepus europaeus, Pallas 1778). We investigated in captive brown hares experimentally whether these effects could result from an undersupply of niacin due to a suspected maize-biased diet in such areas. We repeatedly mated adult female hares, fed ad libitum either with a niacin deficient pellet mainly consisting of maize plant parts, or with the same pellet enriched with niacin to meet physiological requirements. We measured effects of the experimental feeding on body mass of females, reproductive output, growth and survival of leverets. We found significantly higher body mass of females fed the control pellet, and faster body mass gain of their leverets until standardized weaning. We found no significant difference between niacin deficient and control diet groups in reproductive output of females and survival rates of leverets. Our results show that even a diet severely depauperate of niacin affects reproductive success of female brown hares only slightly, presumably because of sufficient conversion of tryptophan to niacin, or of additional supply of niacin by caecal microorganism.

1,2Mamun Abdullah Al*, 2Md. Didarul Alam, 2Aysha Akhtar, 3Abu Hena Mustafa Kamal, 2Md. Shafiqul Islam, Md. Wahidul Alam, Rahman Muhammed Forruq, M Muslem Uddin & Henglong Xu 1Laboratory of Microbial Ecology, Ocean University of China, Qingdao 266003, China 2Faculty of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh 3Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Campus Bintulu Sarawak, 97008 Bintulu, Sarawak, Malaysia *[Email: mamun.imsfcu16@gmail.com]

1,2Mamun Abdullah Al*, 2Md. Didarul Alam, 2Aysha Akhtar, 3Abu Hena Mustafa Kamal, 2Md. Shafiqul Islam, Md. Wahidul Alam, Rahman Muhammed Forruq, M Muslem Uddin & Henglong Xu 1Laboratory of Microbial Ecology, Ocean University of China, Qingdao 266003, China 2Faculty of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh 3Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Campus Bintulu Sarawak, 97008 Bintulu, Sarawak, Malaysia *[Email: mamun.imsfcu16@gmail.com]

Large plots of maize in agricultural landscapes are associated with reduced reproductive output of females and impaired population development of freeliving populations of European brown hares (Lepus europaeus, Pallas 1778). We investigated in captive brown hares experimentally whether these effects could result from an undersupply of niacin due to a suspected maize-biased diet in such areas. We repeatedly mated adult female hares, fed ad libitum either with a niacin deficient pellet mainly consisting of maize plant parts, or with the same pellet enriched with niacin to meet physiological requirements. We measured effects of the experimental feeding on body mass of females, reproductive output, growth and survival of leverets. We found significantly higher body mass of females fed the control pellet, and faster body mass gain of their leverets until standardized weaning. We found no significant difference between niacin deficient and control diet groups in reproductive output of females and survival rates of leverets. Our results show that even a diet severely depauperate of niacin affects reproductive success of female brown hares only slightly, presumably because of sufficient conversion of tryptophan to niacin, or of additional supply of niacin by caecal microorganism.

RMR and aerobic capacity. The large degree of individual variation in traits such as metabolic rate, aerobic capacity, starvation tolerance and risk-taking behaviour suggests that there are trade-offs between these traits whichdepending on environmental factors such as food availability and predator abundancecould have an important influence on which individuals survive in wild populations.

Zooplankton are a primary component of aquatic food chain and play an important role in the functioning of aquatic food webs. Seasonal variation in community structures of zooplankton and potential environmental drivers were studied, during a 1-year cycle (summer 2015spring 2016) in subtropical maritime channels systems in the Bay of Bengal, coastal waters in Bangladesh. A total of 32 species representing 25 families, 13 orders and 15 taxonomic groups were identified. Of these species, 23 distributed in all four season of which 8 were dominant species with high contributions of the total communities. Species number was peaked in autumn and fell in summer while maximum abundance was in the winter and minimum in summer. Multivariate analyses showed that there was a clear seasonal shift in zooplankton community structures in relation with environmental conditions. Species diversity and evenness peaked in summer while the high value of species richness was found in autumn. Multivariate correlation (RELATE) and BIO-ENV analysis demonstrated that seasonal variation in community patterns was significantly correlated with temporal shift of environmental conditions and that variation mainly driven by water transparency, salinity, DO, TSS and nutrients. Thus, this finding implies that the zooplankton community represented a clear seasonal shift shaped by environmental drivers in subtropical channels systems.

RMR and aerobic capacity. The large degree of individual variation in traits such as metabolic rate, aerobic capacity, starvation tolerance and risk-taking behaviour suggests that there are trade-offs between these traits whichdepending on environmental factors such as food availability and predator abundancecould have an important influence on which individuals survive in wild populations.

1,2Mamun Abdullah Al*, 2Md. Didarul Alam, 2Aysha Akhtar, 3Abu Hena Mustafa Kamal, 2Md. Shafiqul Islam, Md. Wahidul Alam, Rahman Muhammed Forruq, M Muslem Uddin & Henglong Xu 1Laboratory of Microbial Ecology, Ocean University of China, Qingdao 266003, China 2Faculty of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh 3Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Campus Bintulu Sarawak, 97008 Bintulu, Sarawak, Malaysia *[Email: mamun.imsfcu16@gmail.com]

1,2Mamun Abdullah Al*, 2Md. Didarul Alam, 2Aysha Akhtar, 3Abu Hena Mustafa Kamal, 2Md. Shafiqul Islam, Md. Wahidul Alam, Rahman Muhammed Forruq, M Muslem Uddin & Henglong Xu 1Laboratory of Microbial Ecology, Ocean University of China, Qingdao 266003, China 2Faculty of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh 3Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Campus Bintulu Sarawak, 97008 Bintulu, Sarawak, Malaysia *[Email: mamun.imsfcu16@gmail.com]

We determined metabolizable energy intake (MEI), body energy change and milk production in primiparous, lactating Sundevall's jirds (Meriones crassus) when nursing litters of two to six pups. We hypothesized that milk production was a constraint and that pups in small litters would have a faster growth rate than pups in large litters. We also hypothesized that females with small litters would offset the costs predominantly with metabolizable energy intake while females with large litters would be forced to mobilize more body energy. There was a negative relationship between growth rate of a pup and litter size which would imply that milk production was the limiting factor in pup growth, which supports our first hypothesis. Although there was an increase in maternal milk production with an increase in litter size, there was a decrease in milk intake per pup with litter size. There was a significant correlation between loss in body energy and litter size, that is, an increase in litter size was associated with more maternal body energy loss, which supports our second hypothesis. MEI in lactating females was on the average 35% above that of non-reproducing females and, together with litter size explained 74% of the variance in the growth rate of a pup. Each of these independent variables contributed about equally to the variance.

European hares of both sexes rely on fat reserves, particularly during the reproductive season. Therefore, hares should select dietary plants rich in fat and energy. However, hares also require essential polyunsaturated fatty acids (PUFA) such as linoleic acid (LA) and alpha-linolenic acid (ALA) to reproduce and survive. Although hares are able to absorb PUFA selectively in their gastrointestinal tract, it is unknown whether this mechanism is sufficient to guarantee PUFA supply. Thus, diet selection may involve a trade-off between a preference for energy versus a preference for crucial nutrients, namely PUFA. We compared plant and nutrient availability and use by hares in an arable landscape in Austria over three years. We found that European hares selected their diet for high energy content (crude fat and crude protein), and avoided crude fibre. There was no evidence of a preference for plants rich in LA and ALA. We conclude that fat is the limiting resource for this herbivorous mammal, whereas levels of LA and ALA in forage are sufficiently high to meet daily requirements, especially since their uptake is enhanced by physiological mechanisms. Animals selected several plant taxa all year round, and preferences did not simply correlate with crude fat content. Hence, European hares might not only select for plant taxa rich in fat, but also for high-fat parts of preferred plant taxa. As hares preferred weeds/grasses and various crop types while avoiding cereals, we suggest that promoting heterogeneous habitats with high crop diversity and set-asides may help stop the decline of European hares throughout Europe.

1. Hares are considered to be a valuable game species in most European countries. Hunting needs to be sustainable and sound management of hare populations requires some knowledge of the species' demographic variability, especially regarding the breeding output, which is highly time-and space-dependent and may govern the population size and exploitability. 2. Using shooting bag analysis and placental scar counts, mean fecundity and leveret survival were estimated at four study sites with contrasting hare numbers and density trends. These demographic parameters, harvest rates and adult natural survival rates (from the literature) were incorporated into a matrix projection model to analyse the population growth rate (λ) sensitivity and to derive indices of sustainable harvest rate (ISHR, i.e. rates compatible with λ ≥ 1). 3. The age structure comprised 48-69% young; fecundity varied between 12•2 and 15•0 leverets per breeding female; and 85-100% of adult females bred. These data combined gave a birth-to-autumn leveret survival index of 0•14-0•29 and, when loaded into the matrix model, resulted in simulated λ s that matched the density changes observed in the study areas. The model structure, although simple, accounted for most of the relevant biological information. 4. ISHR was 30% when derived iteratively as a function of mean values of those parameters with largest elasticities (leveret survival and doe fecundity). When environmental and demographic stochasticity were included in the model, the proportion of endangered trajectories where the density threshold was < 1 km 2 over 50 km 2 varied sharply, with small changes in harvest rate or initial population size. Small populations could only sustain ≤ 20% harvest rates. 5. Demographic parameters derived from killed animals during year t can be used a posteriori to understand the species' dynamics and as a baseline to modulate the shooting scheme in year t + 1. An actual sustainable shooting scheme would require an additional real-time local process that, automatically, would take all sources of change in numbers into account. A two-stage management strategy (e.g. first computing a catch-effort estimator of population size based on numbers killed very early in the shooting period, then defining flexible harvest quotas) would help managers to cope with the unpredictable dynamics of the species and resulting fluctuations in hare numbers. 6. Synthesis and applications. The results of this exploratory study suggest that sustainable shooting of hares is possible provided some local data about their dynamics are available and slightly conservative quotas are used. Modelling approaches have potential in assessing the latter, but also as a check on the coherence of the estimates of the former (comparison of observed and modelled λ).

The food habits of the endangered Italian hare have not received adequate attention from researchers. In this study, the diet composition of this species and its seasonal variation were assessed by analysing faecal pellets in a semi-natural landscape in the south of Italy. The results showed that hares feed on 62 species of plants during the year, with a conspicuous presence of herbaceous ones (e.g., Trifolium pratense , Brachypodium sylvaticum , Festuca arundinacea ) as these occurred at high frequencies in most of the faecal samples. In spring, diet composition was characterised by a high percentage of Graminaceae ( > 37%). In the other seasons, hares also included fruits (e.g., Prunus spinosa , Pyrus piraster , Malus sylvestris ), which, in autumn, accounted for > 27%. There were significant differences among seasons (p < 0.001) in terms of Margalef ' s richness, Shannon diversity, and Buzas and Gibson ' s evenness. The smallest values of richness and diversity were observed in spring. Dietary overlap was low between spring and the other seasons; conversely, there was substantial overlap ( > 70%) in the diets during the other seasons with a more pronounced similarity between summer and autumn (S ø rensen, C s = 0.80; Morisita-Horn, C MH = 0.73).

The food habits of the endangered Italian hare have not received adequate attention from researchers. In this study, the diet composition of this species and its seasonal variation were assessed by analysing faecal pellets in a semi-natural landscape in the south of Italy. The results showed that hares feed on 62 species of plants during the year, with a conspicuous presence of herbaceous ones (e.g., Trifolium pratense , Brachypodium sylvaticum , Festuca arundinacea ) as these occurred at high frequencies in most of the faecal samples. In spring, diet composition was characterised by a high percentage of Graminaceae ( > 37%). In the other seasons, hares also included fruits (e.g., Prunus spinosa , Pyrus piraster , Malus sylvestris ), which, in autumn, accounted for > 27%. There were significant differences among seasons (p < 0.001) in terms of Margalef ' s richness, Shannon diversity, and Buzas and Gibson ' s evenness. The smallest values of richness and diversity were observed in spring. Dietary overlap was low between spring and the other seasons; conversely, there was substantial overlap ( > 70%) in the diets during the other seasons with a more pronounced similarity between summer and autumn (S ø rensen, C s = 0.80; Morisita-Horn, C MH = 0.73).

a plateau which is not further exceeded. With increasing litter size of up to three young, however, milk-intake per juvenile decreases. These and further observations led us to hypothesize that female hares encounter physiological limits during lactation. What is the nature of these physiological ceilings, and which factors influence maximum energy turnover? To answer these questions, we performed a study in laboratory-housed female European hares raising three young.

Charles Darwin, alike his coevals considered reproducing animals to be limited by food availability in their environment. However, recent studies on mammals and birds have demonstrated that, even when food is abundant, energy intake of animals with high nutrient demands, such as lactating females, may reach a limit. It is still not fully understood what the nature of physiological ceilings is, and which factors influence these limits. Two main approaches are available to explain limits to energy turnover. The first concept suggests that certain, primarily morphologically imposed constraints (e.g. the extent of the gastrointestinal tract, the capacity to dissipate heat or the functionality of muscles) might be limiting for mammals. In this view, physiological limits would represent constant traits that have evolved as an adaptation to average resource availability and reproductive investments. The other framework available to explain energetic ceilings refers to life-history strategies. Ever since R.A. Fisher followed by the work of D. Lack, L. C. Cole and, particularly, G.C. Williams in the last century, it has been suggested that investment into current reproduction may conflict with future reproduction and survival. Assuming that operating at peak rates of energy turnover has a physiological cost (the exact nature of which still remains to be uncovered) it will serve the interest of an individual to approach physiological limits during reproduction only if the reproductive value of the current offspring is relatively high. To date, we however do not know whether reproducing mammals regularly operate at their physiological limit, or well below in order to not overly compromise their own survival and future reproduction. In the latter case, reproducing females may maximise their fitness by evaluating costs and benefits of each reproductive event before approaching metabolic ceilings.

European hares (Lepus europaeus) in central Europe have high energetic costs of reproduction, mainly due to precocial, rapidly
growing young that rely largely on energy-rich milk. Thus, hares in this climate build up large fat stores during winter that are then
gradually depleted during the spring-to-autumn breeding season. We hypothesized that the diminishing fat stores of females over
the breeding season might affect resource allocation, peak energy assimilation during lactation or the total investment in
offspring. Therefore, we measured energy intake, milk quality and milk production throughout lactation in spring, summer and
autumn in females raising (size-manipulated) litters with three young each, under a natural photoperiod but at buffered ambient
temperatures inside our facility. Over the course of the breeding season, the amount of milk production remained constant, but
the fat content of the milk decreased. Hence, total energy transfer to young decreased significantly in autumn. By using
undecanoic acid as a tracer of body fat mobilization, we were able to show that milk fat partially originated from maternal fat
stores, particularly in spring. The peak sustained energy assimilation rates of lactating females were significantly higher in
autumn, due to increased rates of food intake. We conclude that fat stores allow female hares to downregulate energy intake and
expenditure early in the breeding season, whereas late breeding forces them to reach peak energy intake levels. Accordingly, we
suggest that in hares, peak energy turnover during lactation varies with the availability of fat reserves. Limits to the sustained
metabolic rate serve as variable constraints on reproductive investment. Thus, there might be a trade-off in energetic costs to
mothers rearing early versus late litters in the year.